REGRESSION ANALYSIS RESULTS:

I’ve had a couple glasses of vodka and pressed a few buttons on the laptop. The Regression Analysis for the set of data is complete. Thank you everyone for contributing and for your suggestions. The results are as follows:

In a nutshell, based on the data provided, the only substantial variables impacting MPG are % Hwy and Driving Style. Yielding an overall Correlation of 79%, this means that these two factors, when combined, explain about 2/3 of the variance between average MPG among RX-8 owners. Relatively speaking, that’s actually very good. Other factors such as using AC, windows open, and Octane also impact MPG, though to a much lesser magnitude. The other variables provided……….no such luck. Model and Tranny I could not use because almost everyone has the 6-Speed GT. One comment regarding Miles to Date. As a particular owner adds miles on their car, it certainly appears that their individual MPG increases, from what I’ve read on other threads. However, when looking across many owners, it is NOT readily apparent that those with fewer miles get worse MPG than those with more miles on their cars. It tends to get washed out by the other, more significant variables. Please see below for the Correlations associated with each of the inputs you provided relative to MPG. The first Correlation factor of 79% for “Regression” is the correlation resulting from including the both % Hwy and Driving Style simultaneously. Also, shown below is an updated MPG vs % Hwy graph

http://www.rx8club.com/attachment.php?attachmentid=5941&stc=1

mod edit : data gathering and discussion thread http://www.rx8club.com/showthread.php?p=149915#post149915

Here's the MPG vs % Hwy graph

http://www.rx8club.com/attachment.php?attachmentid=5942&stc=1

MPG ESTIMATION:

One of the most important outputs of the Regression Analysis is an actual equation that can be used to estimate what someone’s MPG would be, based on their % Hwy and Driving Style. This can be very useful in a couple ways:
1. A current owner can assess, based on their % Hwy and Driving Style if they fall near the Estimated Mileage using the equation. If their MPG is far below the Estimate (say 2 MPG), then either their own estimates of % Hwy or Driving Style may be somewhat off, or some other factors not yet discovered may be coming into play.
2. For a non-RX8 owner who is contemplating getting the car, this Regression equation can be used to Estimate what their MPG might be, given their % Hwy and Driving Style.

Here is the Equation and an Example of how it works:

Estimated MPG = 18.23 + (5.22 * % Hwy) - (1.19 * Driving Style)

Note: For Driving Style ----- Use 1 instead of A, 2 instead of B, 3 instead of C

For someone Driving 80% Hwy with a Driving Style of B (2), the calculation would be
18.23 + (5.22 * 0.80) - (1.19 * 2) = 20.1 Estimated MPG

Below is a graph of each response Actual vs Estimated MPG. To see your data point, get your observation number from the raw data table below the graph.

http://www.rx8club.com/attachment.php?attachmentid=5943&stc=1

Here's the raw data

http://www.rx8club.com/attachment.php?attachmentid=5944&stc=1

One thing to note: Though it looks like % Hwy and Driving Style are the most important determinants of MPG, there certainly may be other variables related to driving conditions/habits which are worth considering. For example, the following have also been suggested:
- Average Highway Cruising Speed
- Average Speed (My favorite preference)
- Altitude
- Updated responses based on more mileage on the cars.

Avg Hwy Cruising Speed may be quite useful. As was pointed out, someone who cruises at 85 mph will get far less MPG than someone cruising at a constant 55 mph. The couple problems with this variable are that for many people (including me), it’s hard to estimate an Avg Hwy Speed. I go anywhere from 55 – 85 depending on traffic, which may yield quite different MPG than someone who just travels at a constant 70 mph. Also, to estimate the average cruising speed would really be a rough ball park number.

I think using Average Speed would probably turn out be the most important variable. It involves NO subjective estimate, and is something which CAN actually be measured. Overall it’s a much better proxy for City/Hwy % driving. One of the biggest problems using % Hwy that I have found while analyzing the data is that it is a subjective estimate, with no hard data behind it. When something is a judgment call, rather than actually measured, it introduces all kinds of problems and judgment error, thus reducing its effectiveness. (That’s also one reason I only included 3 different categories for Driving Style rather than 5 or more).


There are definitely some outliers relative to the estimates, and there is certainly room for improvement. With this idea of improving the analysis, we have to consider a couple things:
1. The ease and feasibility of obtaining the new, reliable information.
2. At this point, people may be sick of this MPG dissection and want to put it to rest.
3. Amount of participation we’ll get.


In conclusion, it looks like significantly improving MPG may be fairly difficult. Based on the data provided, the analysis shows MPG is mostly determined by driving conditions. The roads people drive on (traffic congestion, lights, etc) can’t really be changed, and I would assume people don’t really want to alter their driving style, especially with a car like the RX-8. If anyone has any comments on the analysis or further suggestions regarding understanding the drivers of MPG, I’d really like to hear.

Interesting Finding:

One BIG outlier in the Actual vs Estimate Graph is the last observation (canzoomer). After doing a bit of forum reading a little while ago, I just discovered he's done some significant work on his engine. Both HP and Torque increased substantially. This is likely one major reason for canzoomer's Actual MPG so much less than the Estimated MPG. I was hoping there was some "external" factor unique to canzoomer's situation that would explain such a large deviation. Perhaps the power increase came at the cost of MPG:)

I'm glad I finished my statistic classes to make sense of all the information.

Good work.

Originally posted by norton
MPG ESTIMATION:


2. For a non-RX8 owner who is contemplating getting the car, this Regression equation can be used to Estimate what their MPG might be, given their % Hwy and Driving Style.

Here is the Equation and an Example of how it works:

Estimated MPG = 18.23 + (5.22 * % Hwy) - (1.19 * Driving Style)

Note: For Driving Style ----- Use 1 instead of A, 2 instead of B, 3 instead of C

For someone Driving 80% Hwy with a Driving Style of B (2), the calculation would be
18.23 + (5.22 * 0.80) - (1.19 * 2) = 20.1 Estimated MPG

Below is a graph of each response Actual vs Estimated MPG. To see your data point, get your observation number from the raw data table below the graph.


Looks like a good correlation. Unfortunately, it does not correlate with the EPA estimates, which suggest a spread of 20-28(!) mpg highway. It seems to me their projections are about 4mpg too high. I wonder if they tested the vehicle before the detuned fuel maps or would be interested in retesting based on this data.

Norton,
This type of analysis is very hard to do with subjective data input such as percent highway driving and driving style. The results are surprisingly good. This looks like it was a "simple" linear correlation of the various factors, one at a time. Do you have any insight as to whether some factors are more important if they are entered as the square of the term, or a combination of factors? For example, the combination of driving style 3 and city driving may be much worse than highway driving and driving style 3. Is the data set good enough to support further analysis?
Ron

that is absolutely beautiful
great work
________
Mercedes-benz 240d specifications (http://www.mercedes-wiki.com/wiki/Mercedes-Benz_240D)

Nubo: You gave me an idea. Based on the regression analysis equation above, I've put together the resultant "REVISED" MPG Estimates. It's actually very simple algebra. Please see the little table below, at the bottom of this post:

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This type of analysis is very hard to do with subjective data input such as percent highway driving and driving style.

Ron: I couldn't agree with you more regarding the subjective data. Per my comment above regarding subjective data, ............



This looks like it was a "simple" linear correlation of the various factors, one at a time.

Ron: The correlation, one factor at a time was only a minor aspect of the entire analysis. More enlightening, I believe, was the regression information which followed where multiple variables were assessed.



Do you have any insight as to whether some factors are more important if they are entered as the square of the term, or a combination of factors? For example, the combination of driving style 3 and city driving may be much worse than highway driving and driving style 3. Is the data set good enough to support further analysis?

Ron: The square of the term I did not try.
I did try a combination of variables. In fact, in the Multivariate Regression analysis, I first started with all the various inputs everyone gave me, looking at them simultaneously. Then I weeded out those variables which were not too significant, and was left with % Hwy and Driving Style as important to determining MPG.

Per your question regarding your example, please see the little table below. I believe the regression model addresses exactly the scenario you describe.



Is the data set good enough to support further analysis?

Ron: Well, it's pretty good data. I was hoping to have another 10-20 observations. It would have helped reduce the impact of the few outliers. Also, there is the shortcoming of the subjective data. I suppose there's more that could be done with the data, though I'm not sure what people would want to see/try.

http://www.rx8club.com/attachment.php?attachmentid=5995&stc=1

I stand in awe of this man! Not only a math wiz, but the spelling and grammer! Bravo!

Uhhhh. Wut'd yuo said I wuz doin?

Originally posted by norton

Ron: Well, it's pretty good data. I was hoping to have another 10-20 observations. It would have helped reduce the impact of the few outliers. Also, there is the shortcoming of the subjective data. I suppose there's more that could be done with the data, though I'm not sure what people would want to see/try.

First, excellent statistical analysis project.

Second, it occurs to me you could simply revisit the topic occasionally to collect more inputs as time goes by and accumulated milage increases. When I get an 8 in another few months, and after I've collected some observations, I'll certainly volunteer some data...

Finally, along the lines of using "cruising speed" as a factor, I think you're suspicions are correct. In every car I've owned, I've noted a strong correllation to MPG and speed... on a tank of gas, I've noted probably on the order of 2-3 MPG, depending on my adherence to the speed limits :D

SpacerX:
Sure, I would be very happy to occasionally rerun the model based on new data. If anyone wants to update their response after more mileage has accumulated on their car, please do so. Or, if anyone wants to provide data for the first time, that's fine too. Rerunning and updating everything is a relatively easy job now that the analytical infrastructure is in place........ basically two glasses of vodka, one joint, and a few computer keys to press.

All in all, at this point I feel comfortable that we have determined a couple things, though not too surprising:
1. GrandMa driving improves mileage.
2. Boring highway driving yields the best mileage.

This is true among any car, though perhaps more so with the RX-8. I think the interesting thing is that no other factors were determined to be significant thus far.

Originally posted by klegg
I stand in awe of this man! Not only a math wiz, but the spelling and grammer!

:p

Great analysis.

Originally posted by Nubo
Looks like a good correlation. Unfortunately, it does not correlate with the EPA estimates, which suggest a spread of 20-28(!) mpg highway. It seems to me their projections are about 4mpg too high. I wonder if they tested the vehicle before the detuned fuel maps or would be interested in retesting based on this data.

The sticker on my AT reads 18 to 25.

Here's an excerpt from the government's web site regarding the window sticker figures.

"Manufacturers test pre-production prototypes of the new vehicle models and submit the test results to EPA. EPA re-tests about 10% of vehicle models to confirm manufacturer's results. The vehicles are driven by a professional driver under controlled laboratory conditions, on an instrument similar to a treadmill. These procedures ensure that each vehicle is tested under identical conditions; therefore, the results can be compared with confidence."

The window stickers also say
"Results reported to EPA indicate that the majority of vehicles with these estimates [18 - 25] will achieve between
15 and 21 mpg in the city, and between 21 and 29 on the highway."

Fortunately, I've been getting good gas mileage and seem to fit right in with the analysis' conclusions. Because of a speeding ticket I received (that will be dismissed if I don't get any more this year), I have kept the speed within the posted limits via the cruise control.

The slower speed has taught me a lesson about speed vs gas mileage and now that premium gas is quite high, I'll probably continue "taking it easy". One good thing about driving slower than usual -- I see a lot more people oogling my Winning Blue.

Norton deserves an A for effort, but In the end, his lengthy analysis only confirms the obvious. I think most people would have come to that conclusion without much effort.

Hard driving spends more fuel.
Highway driving gives better mileage than city driving (as indicated by all MPG reports).

Tell me I'm wrong, but that's pretty damn obvious.

Norton,
Thanks for your comments. Another potential "independent" variable is the number of cold starts. I did this type of analysis for another car many years ago and a cold start is devastating to the gas mileage. I think that this would be especially bad for the RX-8 since it apparently runs rich at low rpm and apparently even more so at start-up based on all of the flooding comments. Hope that this helps.
Ron
PS
Do you have an estimate of the error band? This is something that is not eassily obtainable from seat of the pants analysis.
PPS
What happens if you exclude data from the analysis that is "bad" for cause?

I have most of my gas slips with calculated mpg @ odo reading with 4600 miles on my car. Another variable is the VIN. Mine is 00502, significantly earlier than those in your study. Would you like to be flooded with more data? cc

I have most of my gas slips with calculated mpg @ odo reading with 4600 miles on my car. Another variable is the VIN. Mine is 00502, significantly earlier than those in your study. Would you like to be flooded with more data? cc

If you have more data, sure, post it up. You can use the survey in the "other" similar thread where I was collecting the data. By the way, VIN was collected and considered in the analysis. (Please see the data table in the 4th post of this thread). Turned out no to be significant.

Norton deserves an A for effort, but In the end, his lengthy analysis only confirms the obvious. I think most people would have come to that conclusion without much effort.

Squidward: Tartar Sauce! Yes, you are correct. I said the same thing ---- All in all, at this point I feel comfortable that we have determined a couple things, though not too surprising:

However, in addition to the obvious there were some other interesting conclusions:
o We now have an idea of How Much Hard Driving reduces MPG and How Much Hwy Driving improves MPG.
o Given an individual's % Hwy and Driving Style, they can see how they "fit" with the rest of the pack.
o I think it's probably safe to assume the EPA estimates are exaggerated by a couple MPG.
o Importantly, we can safely omit other variables we were wondering about signficantly impacting MPG (eg. VIN).

"Manufacturers test pre-production prototypes of the new vehicle models and submit the test results to EPA. EPA re-tests about 10% of vehicle models to confirm manufacturer's results.
mngpao: Can you please provide a link for the above quote. I wanted to read up a bit more on this. I found a similar article, but it implied all new models are tested by the EPA. Here's the link.http://autorepair.about.com/library/weekly/aa022501d.htm
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Do you have an estimate of the error band? This is something that is not eassily obtainable from seat of the pants analysis.
Ron: The Standard Error is about 1.5. This is an output of the Regression Analysis, but I didn't think anyone would be interested.
I did try dropping two outliers. The resultant estimates increased about 0.2 MPG. Actually, this is an important point because it illustrates that the Estimate Equation is very stable. By the way, I also added 2 new observations.... No change to the results though, other than decreasing the Standard Error.

great

Now, that regression of .22 on octane, what octane is best for MPG?

Well, I don't know what you can do with my info, but my RX-8 is for weekend fun (I have other cars and trucks for day-to-day). I go to redline most times off the line in town(1st only), use 97 octance, and hit over 100mph at least once every time I hit the freeway (but not for long), and I get about 15 mpg. I hate the gas mileage, but if I could ever stop hitting the gas pedal, I could probably approximate the EPA, or get close.

But you know what ? I really don't care, because those few minutes over legal are so fun !!!!

AND last week, I was actually driving sane, doing 40 in a 35, coming up to a light that was green, a minivan in the RED lighted left turn lane that was STOPPED decided to get in my lane about 30 feet in front of me, and I swerved to avoid her ! Any other car I have driven, including my Corvette (maybe...)would have rolled. I got sideways rubber on all 4, but other than 10 years off my life based on my heart-rate, no damage.

Thanks Madza !

Squidward, you are right. Occam's razor holds true once again.


Originally posted by Squidward
Norton deserves an A for effort, but In the end, his lengthy analysis only confirms the obvious. I think most people would have come to that conclusion without much effort.

Hard driving spends more fuel.
Highway driving gives better mileage than city driving (as indicated by all MPG reports).

Tell me I'm wrong, but that's pretty damn obvious.

Originally posted by norton
Interesting Finding:

One BIG outlier in the Actual vs Estimate Graph is the last observation (canzoomer). After doing a bit of forum reading a little while ago, I just discovered he's done some significant work on his engine. Both HP and Torque increased substantially. This is likely one major reason for canzoomer's Actual MPG so much less than the Estimated MPG. I was hoping there was some "external" factor unique to canzoomer's situation that would explain such a large deviation. Perhaps the power increase came at the cost of MPG:)
Actually the opposite.
I did not count the 2.5 tankfuls I have run with mods installed and active.
So far, using MY driving style, I have run 2 tanks on highway, and one half in city.
On the highway, where I generally run at 140-145kmh, I got just slightly better mileage than my previous tanks. About .5l/100 better.
In city driving, where I tend to rev higher more often, I got quite a bit better mileage, at around 1.5l/100 better.

As it is not a large enough sample, and as this study was on cars that are stock, i did not include my recent tankfuls.

I do not believe my mods will have a major impact on highway mileage, and for city mileage , while there is definite gain, that is dependant mostly on driving style.
The only areas where we leaned out the mixture was above 6,000rpm.
For this to be a significant factor you have to get on the gas and shift above 6,000 with some frequency.

If you drive more gently, and shift below that then i expect to see little difference in economy.

Originally posted by SpacerX
First, excellent statistical analysis project.

Second, it occurs to me you could simply revisit the topic occasionally to collect more inputs as time goes by and accumulated milage increases. When I get an 8 in another few months, and after I've collected some observations, I'll certainly volunteer some data...

Finally, along the lines of using "cruising speed" as a factor, I think you're suspicions are correct. In every car I've owned, I've noted a strong correllation to MPG and speed... on a tank of gas, I've noted probably on the order of 2-3 MPG, depending on my adherence to the speed limits :D

Exactly right. I ran one tankful on the highway, and kept rpm below 4,000 ( speed below 125kmh)
I got about 2L/100 better mileage than my usual speed of 140+kmh and 4,400rpm.

Another factor to consider on the highway driving is that just below 4,000rpm the secondary intake runners are opened, and fuel consumption will climb at an rpm range above that.

This car will make mediocre mileage when driven at speed limits, and with a gentle foot.

And horrible mileage when you go faster.

Norton: the link I quoted was found at www.fueleconomy.gov

Sorry I didn't include it with my post. That URL is on the window sticker in the bottom of the border that surrounds the MPG notice.

Now, that regression of .22 on octane, what octane is best for MPG
RodsterinFL: Based on the data provided, the correlation of .22 means that Octane has little to do with MPG. I tried a lot of different approaches in the regression analysis with respect to Octane because I know that this was a topic of much discussion. I could never achieve any result showing Octane measurably impacts MPG. So I cannot answer your question. From what I recall, I believe you were one of the major proponents of using 87 Octane and had originated a thread on this issue. Right??

I did not count the 2.5 tankfuls I have run with mods installed and active.
canzoomer: Sorry. My bad for assuming your response was post engine mods.

Squidward, you are right. Occam's razor holds true once again.
newport8: Occam's razor Never heard that term before. Pretty funny. In case anyone is interested, here's a link for the definition, cartoon included: http://zebu.uoregon.edu/~js/glossary/occams_razor.html I guess for those people that think that the analysis showed ONLY what was obvious, then this is true.

In the statistical world, it's essentially leaving all those extra variables to your error term.

If you normalized MPG for % highway time and just plotted a simple histogram, I bet you'd get a standard bell curve. You might even get one without normalizing. I think the problem is that, no matter how precisely Mazda tries to build its rotary engines, there's going to be a some inevitable variation present, which will show up in a standard distribution of MPG, HP, or whatever. Some people will get lucky and get an engine that is at the top end of the curve. Others will be unlucky and get one at the bottom. But most people will get one at the mean, median and mode.

Originally posted by norton
newport8: Occam's razor Never heard that term before. Pretty funny. In case anyone is interested, here's a link for the definition, cartoon included: http://zebu.uoregon.edu/~js/glossary/occams_razor.html I guess for those people that think that the analysis showed ONLY what was obvious, then this is true.

newport8: Yes, I agree with you about the normal distribution. Hopefully this inevitable variation in rotary engines would yield only a slight variation in MPG, given identical driving and other conditions. It's hard to assess though, because as you said, the Standard Error encompasses a slew of factors other than %Hwy and Driving Style.

Originally posted by Squidward
Norton deserves an A for effort, but In the end, his lengthy analysis only confirms the obvious. I think most people would have come to that conclusion without much effort.

Hard driving spends more fuel.
Highway driving gives better mileage than city driving (as indicated by all MPG reports).

Tell me I'm wrong, but that's pretty damn obvious.

It may seem obvious now, but there was protracted and heated debate when the first of us got our cars to look for other reasons in our different MPG results. The common culprit was ECU changes. We had no way to assess driving style until Norton put this together. STrange tho it may seem, it was not immediately obvious at the time.

Um, in reference to the above Squidwardian quote, it is the pretty (doggon) obvious factors, those very things, that cloud the original persuit of determining the not-so-obvious factors that also affect mpg.

VIN (build date) <<--- most sought-after factor
Total vehicle mileage
MT .vs. AT
Aero kit / rear spoiler
Strakes
Front / Rear rotary accents
Color
Marital status

I would love to see if distance traveled for daily commute is a significant factor. I have read several threads where a short trip in a cold environment will result in below average consumption. I travel 7 km all highway (except for a total of 10 city blocks with 3 stops). This was true, it would significantly skew the results since I would present as 90% highway but horrendous MPG. Ambient temperature (overnight and during travel) is another factor that should be investigated when trying to account for lower MPG. fimichael reports a drop of 2 L/100 km since temperatures have dropped below freezing.

I no longer have an 8, I returned it in September because of fuel consumption issues not because of lower HP. If Mazda can promise 12L/100 km hwy and around 10.5 city, I'll get another one. BTW it's not the cost that I mind, it's the fact that at 15L/100 km this car is less efficient than many SUV's.

So, buy an SUV. Since when was the 8 supposed to be an economy car anyway? I suppose an SUV with a lame power plant (typical, but there are exceptions) would have better mpg. Go for it!

Your short repeated highway useage is exactly the clouding of the issue that I was refering to. The pitfall of statistical analyses.

Originally posted by Racer X-8
Your short repeated highway useage is exactly the clouding of the issue that I was refering to.

The question that I was asking, is it the short runs or cold temps or both. It would appear to be combination of the factors but the stats may show us that temp has more to do with it then distance. My current car (Integra) shows only a moderate difference in fuel consumption when doing the short stints and driving to Toronto and back (9.8L/100km vs 10.8L/km) while I see a drop of >1.5L/100km between summer and winter. The rotary may or may not follow this pattern.

So, buy an SUV. Since when was the 8 supposed to be an economy car anyway?

Well, since you asked ;) Mazda says 9.2 L/100 km highway and 12.8 city. I never expected an econocar but 15L/100 km highway!!! My neighbours Pathfinder v6 4x4 is no beast but is no slouch either and gets better numbers. The best I've seen posted here is 10.5 highway but most are in the teens with some poor sod getting high teens. And yes it is possible to get decent fuel efficiency with a high reving, nimble sports car, ie S2k. The 8 is still the car that I want most but we all have to decide for ourselves what is acceptable. All I said was if Mazda can give me 12 hwy, I will take it, but 15 I will wait for something else. I was hoping that this thread was going bring a solution to my dilema but alas it looks like I will have to wait a little longer.

At least it brings an answer to your dilemma, but alas not the answer you were hoping for.

Someone (CZ?) posted that the stock ECU leans out in the 4k rpm region, so a remapped ECU wouldn't help MPG much unless retuned for lower than 4k rpms. So, where next for improved MPG? CAI? Larger rear tire radius? Higher differential ratio? Catbacks? Which ones? How?

As far as SUV's go I can say that the H2 I test drove for 2 days was ranging about 13.5 mpg with 850 miles on it. My RX-8 with 1,800 miles on it is still only getting 14-15.5 mpg. Both were driven in same conditions and terrain. So Racer X-8 are you suggesting that we should expect to have our cars pelted with rocks and acid by enviromentalists any time soon? And as a side note the mpg were not listed on the H2 because of its' weight class. I know that I am not competing with the H2 in its' weight class but it seems that I am in fuel consumption. Apparently the EPA standards were done for a car not driven in typical city driving conditions becuase, as I've read on the forum, most of the people posting about fuel economy are driving a good portion of the time in the city and not on the highway. I didn't tell Mazda what to post for mpg they did that all on their own. I just want them to live up to the standard they already set. Let me know if that is so wrong.

On a daily basis I do not have to get on the freeway to drive. I do drive roughly 45 mins to work. My car has always gotten 175 to 180 miles before te idiot light comes on. Roughly 14 mpg. It has never changed. Today I went roughly 276 mile before it came on. That is 14 city, 21 hwy. The suprising thing was that on the hwy i was never under 70, and was mostly over 90. The gas mileage sucks, but I was suprised at todays hwy mpg.

Holy resurrected threads, Batman!

The only thing surprising about your newly-achieved highway mileage is that it was as HIGH as it was, since you claim to be driving around at 90+.

It suprised me also! The car just seems to like to go fast.

I wonder what kind of cars and what kind of milage executives and CEO or the 8 big oil companies are getting? Any known stats?

Just a thought... My LR3 landrover weighs almost three tons with me driving and my RX-8 about 55% of that. The rover gets 14mpg and the Mazda 17mpg. Some how I seem happier with the LR3's milleage... though both are at about the EPA city range. On the highway the rover gets 17.5 (close to it's 18mpg rating, the Mazda get's 21-22 hwy - 3mpg short of its hwy rating. - I bet if sixth gear was just a little taller the MPG in real life would match the current EPA numbers. I'd like to turn 3000 RPM at 75MPH - not 3750.

I'm not really that upset about the milleage on the eight either. For the money I saved vs. other cars the effective miles per gallon is more like 22-28 mpg city instead of 17.

I get 22-24 on the highway with air running. Not sure about it off, its been blazing hot here.

I get 22-24 on the highway with air running. Not sure about it off, its been blazing hot here.

Same here... Hot, that is. I beat the Monroney sticker in cooler months with no AC (I don't have the numbers in front of me, but I think my high was 25.5MPG, but even that used a LITTLE bit of AC for demisting) and now I'm right at the rated MPG, at least on the highway, even with the AC on. Ranges from 23.5-24.8. That high tank actually pushed me over 400mi on one tank, which is about as good as I'd ever expect from this car. Just slightly less range on one tank than my Mazda6S 5spd achieved on ITS high tank, but of course that car had a smaller tank.

For the record I do 72-77mph, depending upon the posted limit... I've got more to lose than just some points on my license and higher insurance if I get speeding tickets.

My MPG is nowhere near the numbers bandied about here. I get about 16 mpg :( with about 80% rural driving. I haven't been driving the car hard either because I'm still in the break-in period. A/C is blasting all the time, though, because I can't stand the California heat. :crazy:

I hear a lot that the MPG improves with time. I'll be tracking my usage the next few months.

16mpg is quite normal when running around at 3-4k most of the time and never using 5th or 6th except on th ehighway. to get 17-18 you have to use 5th in town at 35 or so and 6th at 42-45 and above

These figures look impressive as tabulated. The actual driving MPG are quite different than your figures.

I've had my RX-8 for 6 months. IT ahs 19,000 miles on it now. The average MPG I get on the car is not even on your graph. At best on the highway I get 13 MPG and city 8 MPG. When it is a mix of city and highway it is around 10 12 MPG.

I bought the car thinking it would be a full time car, but honestly have parked it and only use it on the weekends, due to the MPG and several other problems with the car.

I can see you spent alot of time on this and it is very well organized. But as in anything figures are only figures.

Actual experience is a total different story.

Wow, someone who gets worst then me. I'm getting 12mpg city in the summer, 11.5mpg winter. I wounder if all the reflashs have made the mileage worst then the original car's programing?

I began keeping track of my mpg (each tank) at http://www.fueleconomy.gov/ (click on "Calculate and Share your MPG"). It then shows up when people search for 2005 RX-8 6MT, and then they can see "actual user mileage" in addition to the EPA estimates. I figured this is like a public service of sorts to potential buyers (plus kinda interesting for me to keep tracking of the mileage).

These figures look impressive as tabulated. The actual driving MPG are quite different than your figures.

I've had my RX-8 for 6 months. IT ahs 19,000 miles on it now. The average MPG I get on the car is not even on your graph. At best on the highway I get 13 MPG and city 8 MPG. When it is a mix of city and highway it is around 10 12 MPG.

I bought the car thinking it would be a full time car, but honestly have parked it and only use it on the weekends, due to the MPG and several other problems with the car.

I can see you spent alot of time on this and it is very well organized. But as in anything figures are only figures.

Actual experience is a total different story.

first these are real world experiences posted by forum members.

second- no one that ever drove their 8 actually on a highway for a full tank on cruise at legal speeds in a gear higher than 3rd EVER got 13mpg on that trip. it is IMPOSSIBLE, CANT BE DONE. fill your tank get on the highway at 65 mph in 6th gear with the cruise set. get off at teh nearest fuel station after the ligth come on. there is no way on this green earth you ever get 13mpg like that. people get 9 mpg during AUTOCROSS weekends. 8 in town is BULLSHIT unless you go everywhere in 2nd gear with your foot in the floor board.

If thats how you drive all the time DO NOT come on here and blame your car- its the loose nut behind the wheel that is the problem.

I'm suspicious that a lot of low mpg reports come from people who recently registered and have only a few posts. Hmm...

I'm suspicious that a lot of low mpg reports come from people who recently registered and have only a few posts. Hmm...

...only that the most recent suspiciously-low MPG report comes from someone who registered last year and has around 375 posts.

Not that I believe the numbers, mind you. I call BS on any report that claims teens on the highway and 10-11 in mixed driving. My worst tank was all-city, with lots of stop-and-go and frequent hard acceleration and it STILL exceeded 13mpg.

13mpg on the HIGHWAY? I think not. I nearly DOUBLED that on one of my tanks.

i really mean the car cant do it. youd have to be at 100% or more duty cycle on the injectors or have ahole in your tank both of which would generate multiple CELS

...only that the most recent suspiciously-low MPG report comes from someone who registered last year and has around 375 posts.I was thinking of the one with 8 posts actually.

Not that I believe the numbers, mind you. I call BS on any report that claims teens on the highway and 10-11 in mixed driving. My worst tank was all-city, with lots of stop-and-go and frequent hard acceleration and it STILL exceeded 13mpg.

13mpg on the HIGHWAY? I think not. I nearly DOUBLED that on one of my tanks. I've achieved 10 mpg a couple times... but that was at the track. :D: City I typically get 17, and 23 is the most I've gotten on the highway.

I've achieved 10 mpg a couple times... but that was at the track. :D: City I typically get 17, and 23 is the most I've gotten on the highway.

I have no problem believing ultra-low mileage at the track... But 10mpg in MIXED city/highway? I call shenannigans.

Funny how 23 is the MOST you've gotten on the highway, as I've not had a single all-highway tank BELOW that number (granted this comes from a sample group of about 5 or 6 tanks). Maybe you just drive faster than I do. :)

I have no problem believing ultra-low mileage at the track... But 10mpg in MIXED city/highway? I call shenannigans.

Funny how 23 is the MOST you've gotten on the highway, as I've not had a single all-highway tank BELOW that number (granted this comes from a sample group of about 5 or 6 tanks). Maybe you just drive faster than I do. :)I never had a highway tank above 21mpg. Most of my 80-100% highway driving nets about 20mpg, and this is mostly cruising at 70-75. I don't know how you drive on the highway, but I have a hard time believing people getting 23+ (e.g. 24mpg) on the highway. Maybe if I drove with windows up, A/C off and cruising 65mph, I would maybe then get 22mpg.

I have no problem believing ultra-low mileage at the track... But 10mpg in MIXED city/highway? I call shenannigans.

Funny how 23 is the MOST you've gotten on the highway, as I've not had a single all-highway tank BELOW that number (granted this comes from a sample group of about 5 or 6 tanks). Maybe you just drive faster than I do. :)Yeah - hopefully people don't drive thru town the way I drive at the track. :Eyecrazy:

The 23 is the only time I've actually measured all-highway driving. I averaged 75 on that trip, and much of the terrain is hilly. That affects the mpg since it accelerates in the up-hill stretches. I would guess in Indiana the terrain is much flatter, so you should expect better mpg in that case.

I think a lot of the problems here can be attributed to the fact that one RX-8 can deliver very different mileage than another under similar driving environments. At the same time people are people and will make mistakes or misreport facts which further clouds the issue. The fact that Mazda seems to be dismissing this issue rather then dealing with it leaves us to further speculate. Here is my mileage reading since the car was new. I attribute a slight increase in mileage to summer vs Winter driving, I'll have to wait till next winter to confirm this. See attachment.

I never had a highway tank above 21mpg. Most of my 80-100% highway driving nets about 20mpg, and this is mostly cruising at 70-75. I don't know how you drive on the highway, but I have a hard time believing people getting 23+ (e.g. 24mpg) on the highway. Maybe if I drove with windows up, A/C off and cruising 65mph, I would maybe then get 22mpg.


not like there isnt witnesses to the 24 mpg tanks. i proved to nemesis 8 (lives up your way) tha tit could be done on th eway to sevenstock driving with cruise set at like 78. he was nervous but blown away when we got into the 340 mile range. the first tanks where i proved it to him i actually got 23.99 and he got 24.2 or somesuch.

I would believe this. I drove a 100 mile trip and based on some very rough estimates believe I was getting 20 to 22mpg on the highway. I was driving at a pretty steady speed. This car seems to suck down the gas far more then a piston engine in response to acceleration. Use the cruse control and you can probably hit the 24mpg. When I was enjoying the highway my mileage dropped to 18.

The MPG killer on our '8s is that 4:88 rear end. My FCs would routinely get their best MPG (23-24) cruising at a steady 85MPH, because of their much taller gears (4:10?), even though they were almost 100HP down on the 8. I get 21+MPG on 95% freeways where my speeds range from 50 to 85, usually able to maintain at least 80 on the cc for 1/2 that time. Not what I expected 3 years and 80K miles ago, but then again, I really don't mind the added N/A HP to play with!! (All miles w/ AC - what little there is - on full time.)

DrDiaboloco, Have had 4 REs & MPG always got better, tho not by a whole lot (+.5-1MPG?).

The 23 is the only time I've actually measured all-highway driving. I averaged 75 on that trip, and much of the terrain is hilly. That affects the mpg since it accelerates in the up-hill stretches. I would guess in Indiana the terrain is much flatter, so you should expect better mpg in that case.

Yes, that would be true... Only my two highest highway-only tanks were from eastern Ohio to western NJ, one in each direction, on I-80. If you're not familiar, that is some pretty hilly terrain as Interstates go, esp. the western NJ to mid-PA stretch. Naturally I didn't do the exact same distance in each direction and stop at the same points, but both trips covered more or less the same ground, just a week apart (early May, very little AC use).

Frankly I was surprised the mileage was as high as it was, but it wasn't a one-off fluke. My mileage was slightly worse on flat land (IN and western OH), but it was also raining each time and I've noticed a precipitous drop in mileage on rainy pavement (even keeping speed more or less the same) with this and other cars I've owned.

Any thoughts as to how vehicle mileage (and therefore the "age" of the engine) would affect mileage?

I've read that the rotaries kind of get more and more powerful as the miles pile up (at least that's what they say about the racing engines)... Would one expect mileage to improve or decrease with age?

For the record, my car still doesn't have even 4k miles on it yet, which is why I ask. My two high tanks were both achieved around the 3k point. I don't have my mileage spreadsheet in front of me, but in concept it's very similar to Raptor's, with date, mileage, octane, and driving style/road conditions. If anyone is even remotely curious I'll post it when I get home (several days from now)... Which will help jog my memory and correct possible errors in what I've posted so far as to best/worst mileage, average, etc.

I have heard that the rotary get better with age in regards to both power and mileage, long term reports in magazines seem to confirm this.

Please post you mileage info. I'd be interested to see it. Thanks

Will do. I'm overseas right now but I'll post the info early next week... Once I figure out how to attach a thumbnail like you did. :D

I calculate not by Miles per gallon, but distance before filling tank in comparison to the Mazda 323. The 323 holds about 12 gallons, if full at San Miguel, requires refilling at Frisco. RX-8 holds about 18 gallons, if full at San Miguel, requires refilling at Frisco - but we get there a lot faster - so for half a tank more than the 323, get speeds of 85+, and spend about $10 -15 more for a long trip in air conditioned comfort... yup this one is good! Much better on hills and also in wind, especially evil cross winds near Salinus - One really good note - Frisco gas prices were about 50 cents per gallon less than our local rip-off prices. Cheapest good gas in area - Morro Bay

Umm, my Rx-8 doesn't hold 18 gallons. How is it that yours has an 18 gal tank?

I calculate not by Miles per gallon, but distance before filling tank in comparison to the Mazda 323. The 323 holds about 12 gallons, if full at San Miguel, requires refilling at Frisco. RX-8 holds about 18 gallons, if full at San Miguel, requires refilling at Frisco - but we get there a lot faster - so for half a tank more than the 323, get speeds of 85+, and spend about $10 -15 more for a long trip in air conditioned comfort...

So you'd rather that we stop using accepted mathematical methods of comparing mileage and instead use nebulous "I can make it from point A to point B" tales that mean nothing to anyone who doesn't drive on your route? What relevance does "distance you can travel on one tank relative to a 323" have?

I think the rest of us will stick with "miles per gallon".

I also thought the idiot light came on when there was 3 gallons left in the tank. When the light comes on, I always put in roughly 13 gallons.

Umm, my Rx-8 doesn't hold 18 gallons. How is it that yours has an 18 gal tank?

Ha ha ha... Somehow that part escaped my notice!

I don't have my manual in front of me, but I seem to recall the number is 15.8gal capacity.

Altitude and speed seem to make the biggest difference in my highway mileage. I can get about 25mpg at 7000 feet and above, but keep in mind most of the time I'm only driving about 50-60mph due to the how tight the roads are up there.

Running 80mph through Kansas nets exactly the same mpg as my mixed driving--roughly 21. Normally I drive about 60-70% highway at 5200 feet. I think if I made the same drive at about 60mph, I could get the claimed 24 highway. This leads me to believe that wind resistance is the biggest factor in determining mileage. Engine RPM doesn't even make that big of a difference. A taller rear-end or sixth gear would seem to make a lot of sense on this car, and I don't really understand why it's so short. It probably is mainly to prolong engine life, in exchange for a little lower mileage at 80mph.

Don't know how I got it - tank came with car - will double check holding capacity - that would really make gas usage better since that would only be 3 gallons more than the 323 and yet delivering the same distance - she is a sweet one!

fuel tank capacity is 15.9 and NOT 18

fuel tank capacity is 15.4 and NOT 18

Mazda's website says 15.9 gallons.

I'm a willing victem - if its only 15 that means I am getting really great MPG convers it means my local stations meters may not be accurate and they are posting more gallons then are being delivered -

if you are putting more than 14 gallons in the car when you fill up, you are a madman who ignores the fuel light for a good 30-40 miles

if you are putting more than 14 gallons in the car when you fill up, you are a madman who ignores the fuel light for a good 30-40 miles
Well... Since the light coming on doesn't mean "you're going to run out of fuel in five minutes", this is hardly the work of a "madman".

I understand that most of you are paying less than $3.69-3.21 per gallon of hi test (local Calif. evil prices)- what are some of your prices and how much do you usually spend to fill/top off your tank?

Paid $3.14 today for Shell 93

The last I paid for my gas was $2.83 a gallon. Cost me 39 dollars for 13 gallons of gas. Give or take

Altitude and speed seem to make the biggest difference in my highway mileage. I can get about 25mpg at 7000 feet and above, but keep in mind most of the time I'm only driving about 50-60mph due to the how tight the roads are up there.

Running 80mph through Kansas nets exactly the same mpg as my mixed driving--roughly 21. Normally I drive about 60-70% highway at 5200 feet. I think if I made the same drive at about 60mph, I could get the claimed 24 highway. This leads me to believe that wind resistance is the biggest factor in determining mileage. Engine RPM doesn't even make that big of a difference. A taller rear-end or sixth gear would seem to make a lot of sense on this car, and I don't really understand why it's so short. It probably is mainly to prolong engine life, in exchange for a little lower mileage at 80mph.

You're contradicting yourself a little right there...of course you're going to get better mileage going 50-60 mph (less work done by the engine, less air resistance) than going 80 mph (~4000 RPMs). How hard you work the engine makes a big difference in gas mileage, I think that's a universally accepted fact.

Your tank could be 1000 gallons. The point is moote. You divide the gallons you put in your tank by the miles on your odometer. Given you reset it on every fuel. There is your Miles/Gallon.

75 MPH = 23.8
80 MPH = 24.3
85 MPH = 25 or better

This was what I observed from a 1700 mile trip in June. High temps going through mountain passes too. 4k to 4.5k RPM seems to be the best for continous burns. I believe we get an advantage over a piston driven auto's. The rotars are not turning cranks that have to turn a drive shaft. They tumble with the shaft. The energy stored up in the mass offsets the fuel needed for that RPM. Helicopters use this concept for emergency landings. It's called auto-rotation. In the event of an engine failure, we clutch the engine from the spinning rotars and set blades for no chop. As the chopper falls to the earth the blades are spinning by their own weight. At 100 foot you pitch the blades to full chop. This counters the fall to a light crash at worst. You really get to thinking on a long trip. My girlfriend slept both ways. Memphis to DC, DC to Memphis. On the way back, we left DC at 12:30 P.M. We stopped for lunch for about an hour or so. We were in the driveway at 1:30 A.M. We did cross a time zone and stops for fuel. Not bad.

Just a theory, but my only thoughts to why the dam thing gets better gas mileage at higher cruise speeds. I use cruise control too. I keep a fixed speed as much as possible. I have put 54,000 miles on it. Drives better than it did with 2 miles on it. I get about 18 in the city. Make sure your shifts should be made so that the next gear see's at least 3.2K RPM.

Just a theory, but my only thoughts to why the dam thing gets better gas mileage at higher cruise speeds. I use cruise control too. I keep a fixed speed as much as possible. I have put 54,000 miles on it. Drives better than it did with 2 miles on it. I get about 18 in the city. Make sure your shifts should be made so that the next gear see's at least 3.2K RPM.


Describe what your city driving is like. Stop and go? Lots of ideas? I can't believe people can get this in the city. My city mileage is 12mpg.

Like any other car, there's a single speed in top gear that offers the highest MPG. No way to know what it is in the '8 without consulting a scientific comparison, but I doubt that higher RPM is the answer... And helicopters have nothing to do with it, either. Don't think that I don't understand what you're getting at, I'm a professional pilot with a degree in Aeronautical Engineering and I'm familiar with the aerodynamics involved in helicopter flight (even though I'm not a helicopter pilot).

I've achieved your alleged mileage at 85mph at 72-75mph, and I highly doubt that it'd improve if I ratcheted up the speed by 10+mph. I'm not sure how you can allege to have these scientific numbers at three different speed points, the lowest of which is the minimum needed to complete the trip with the quoted hour-long lunch break... Your average speed over the trip (850mi in 13hrs, not including your break) is effectively the same as mine on a recent highway trip (700mi in 10.7hrs, INCLUDING stops and traffic tie-ups in metro areas and construction sites)... A trip during which I never exceeded 75mph... And in which you claim to have mileage numbers for a speed 10mph higher than that which I was travelling.

Do you see where my skepticism comes from? Drop the hour-or-so lunch break and include fuel stops and somehow I'm still achieving a slightly higher average speed while only going 72-75mph MAX on the road!? Are you REALLY doing 80 or 85mph for a whole tank and coming up with those numbers, or are you just making suppositions?

And these numbers from my end are on a nearly-new car that has theoretically lower MPG than a well run-in car. I'm not trying to be a dick, but something doesn't add up here.

How much does the presence of a passenger effect milage? Luggage? Also does anyone know how many rotations of the wheel we get per rotations of the rotar?

My latest mpg was 14.6. I live 1.7 miles from work so basically, I fire up the motor, let it warm up, drive 5 min, then I'm at work. There was a little bit of highway driving on this tank so if it's all city driving, I'll probably get worse mpg.

2005 AT with 1000 miles on the clock.

first these are real world experiences posted by forum members.

second- no one that ever drove their 8 actually on a highway for a full tank on cruise at legal speeds in a gear higher than 3rd EVER got 13mpg on that trip. it is IMPOSSIBLE, CANT BE DONE. fill your tank get on the highway at 65 mph in 6th gear with the cruise set. get off at teh nearest fuel station after the ligth come on. there is no way on this green earth you ever get 13mpg like that. people get 9 mpg during AUTOCROSS weekends. 8 in town is BULLSHIT unless you go everywhere in 2nd gear with your foot in the floor board.

If thats how you drive all the time DO NOT come on here and blame your car- its the loose nut behind the wheel that is the problem.


Listen kid....I don't bullshit. I have owned several cars and I know what I'm talking about. I don't appreciate your arrogant attitude....

I bought the car because it appealed to me. After being an owner for seven months now I've been able to evaluate the car to its full capacity. OF all that time the car has been in for service six times I shift when I need to and never race the engine. I've have driven the car on the highway for a full trip many times. People like me that have money do go on long trips punk...

I think there is something wrong with my car. Mazda doesn't want to address it. I think the MPG can be atributed to the car having some sort of rotational drag. I found that my car actually slows down on a decline. Brakes hard to right at times. It's on its second set of tires. I've had the brakes checked by brake specialists and they have found thing wrong with the brakes. Mazda blamed the wide tires. I have wide z rated tires on my Mustang and don't have these problems. I'm really not sure what the problem is. I think the rear end mybe out of alignment. I feel Mazda should pay for this as it would seem it came like this from the factory. I've had several cars and have never run into having an alignment during the break in period. this car has had poor MPG right from the time it was bought. I'm disappointed in how Mazda doesn't stand behind their poor quality.

Why would someone waste time whining on this forum instead of getting their car fixed? If anyone really got 13 mpg for highway driving there'd a severe problem with the car. Seriously, the last thing someone would realistically think of doing is complaining on a forum. That kind of BS (plus two set of tires and 13 posts) makes you sound like a troll.
:jerkit:

Listen kid....I don't bullshit. I have owned several cars and I know what I'm talking about. I don't appreciate your arrogant attitude....

I bought the car because it appealed to me. After being an owner for seven months now I've been able to evaluate the car to its full capacity. OF all that time the car has been in for service six times I shift when I need to and never race the engine. I've have driven the car on the highway for a full trip many times. People like me that have money do go on long trips punk...

i am 38 years old. im not a punk and while i may be arrogant its because im right. you can not get that kind of mileage on the highway. period end of story. since you aren't bullshitting then you must be an idiot. i dont care if your rich or poor or what ever kind of people you are. you dont know what you are talking about. your car literally can not pump that amount of fuel on the highway at anything appproaching normal speeds. on a track- sure. if you drive on the highway like its a race track then you are complaining about yourself. and an idiot.

i am 38 years old. im not a punk and while i may be arrogant its because im right. you can not get that kind of mileage on the highway. period end of story. since you aren't bullshitting then you must be an idiot. i dont care if your rich or poor or what ever kind of people you are. you dont know what you are talking about. your car literally can not pump that amount of fuel on the highway at anything appproaching normal speeds. on a track- sure. if you drive on the highway like its a race track then you are complaining about yourself. and an idiot.Sometimes I suspect that people who are reporting bad mileage may just be goofing up on the calculation. I've gotten 10 mpg before, but only at the track.

- Fill up your tank.
- Reset your odometer to zero.
- Drive.
- Fill up your tank again. Note the number of gallons it took to refill.
- Note the number of miles on the odometer.
- Divide the number of miles by the number of gallons.
- Check your work.

Repeat the same process over several tanks to get an average.

Seeing that I have a degree in Mathematics/Computer science I never really considered calculating gas that big of a deal.

It is easy to right off someones poor mileage until it happens to you. The guy above could very well have a issue with mileage and I am sure that as soon as Mazda hears "gas mileage issue" they turned their back on him. This is the big problem with Mazda, the RX gets poor mileage normally. When an RX has a problem which effects gas mileage Mazda instinctively assumes it is just another person complaining about normally poor mileage. The end result is those who truly have problems are never serviced or corrected.

Here is my record mileage to date.

I think there is something wrong with my car. Mazda doesn't want to address it. I think the MPG can be atributed to the car having some sort of rotational drag. I found that my car actually slows down on a decline. Brakes hard to right at times. It's on its second set of tires. I've had the brakes checked by brake specialists and they have found thing wrong with the brakes. Mazda blamed the wide tires. I have wide z rated tires on my Mustang and don't have these problems. I'm really not sure what the problem is. I think the rear end mybe out of alignment. I feel Mazda should pay for this as it would seem it came like this from the factory. I've had several cars and have never run into having an alignment during the break in period. this car has had poor MPG right from the time it was bought. I'm disappointed in how Mazda doesn't stand behind their poor quality.


I had a problem after I lowered my car andchanged the rims. They were supposed to check the caster, camber and toe-in. After I noticed my right rear wearing more than the other tires, I took it in and had all three measured again. Sure enought the right rear had more negative camber. I had them remove as much negative camber from both rears (ended up at -1.2). It hasnt had a problem since.

I am not sure if it was sloppy work that caused the proble, or something that did while driving the car hard. Either way, it was cheap to inspect and to repair. I got everything done at Les Schwab.

As promised earlier... A screenshot of my mileage spreadsheet, with all the detail I think you need to see what sort of mileage my car is getting.

I have broken down some things that may not be immediately apparent, so here are the translations:

In the FUEL column: PREM=91, Mid/Plus=89, Reg=87

In the NOTES column:
Interstate: Means a steady 72-75mph (in 65-70mph zones) for long stretches, broken only by traffic, passing, or other obstruction.
Highway: Means steady 62mph (in 55mph zones), broken up by stop signs, railroad crossings, passing through towns with much lower speed limits, etc.
Local: In-town driving, all at posted 45mph or below. Frequent stop-and-go, minimal redlining... At most one "beep" per trip, predominantly below 5-6000rpm.
Rain: Self-explanatory. Moderate-heavy rain on this particular tank (these are only shown on stretches that are otherwise categorized as "Interstate" as of this point).
A/C: Use of air conditioning is either Light (under 15mins/hr) or Heavy (45mins or more per hour). Even though it is only mentioned on "Interstate" tanks, my last three tanks were all in the "Heavy A/C" category.
Anything Else: Information to remind myself what the trips and conditions were like. Mostly city/state codings.

http://img.photobucket.com/albums/v697/drdiaboloco/MileageCrop.jpg

There is one tank, the most recent one, that is not included in this spreadsheet because it's sitting in the car and I'm too lazy to go get it. :) It would have little effect on the average as it's roughly 19mpg.

I did a 109 mile trip. 84 miles was on 4 lane highway at speed averaging about 70MPH. The remainder of the 25 miles was urban driving.

Averaged 22.5MPG on 91 octane. I had a/c off and sunroof wide open the whole time.

In comparison, I did a quarter tank of complete city driving with lots of stop lights and engine on and offs, 3 people in the car and averaged 16MPG.

In more than 70,000 miles of driving, mostly highway, I have a combined MPG of 21.1 with my best tank of 23.1 and my worst of 17.8.

Driving to Fla, 30 miles of city driving and basically the rest where pretty much highway driving - 24.78 mpg. The next tank of gas was 1/2 highway, 1/2 city while in Fla and it was 21.30 mpg. This is in an unmodified 05 auto RX-8.

Tim

Just did a 70 mile highway trip with gentle crusing and acceleration. I averaged probably 70-75 the whole time on the highway. I got at least 23.1MPG if not a tiny big higher. A/C was not on.

I think the RX-8 can easily meet the EPA highway estimate considering how easy of a test it is. I'm curious how much my mileage would increase by dropping the speed down to 65MPH or so.

I'm about to do a very long highway stint, over a thousand miles, so I should have three fillups on an all-interstate run... Four if you include the top-off at the other end. Unfortunately the AC will be on the whole time and that will roon it, but maybe the return trip will need less AC... I'll report later.

Hopefully very little of that trip will be at 65mph. ;)

Yep I'm about to run about 2500 miles in mine. I hope to average about 22mpg, possibly by slowing down to 70 or so.

In LA traffic and cruising up the 101 freeway north to Pismo Beach, I got 21.24 MPG. Coming back down the 101 and through LA, including getting stuck in the I-91 traffic for an hour, I got 21.9 (all the way out to Palm Springs)! The very next tank, cruising across the desert heat, with the A/C (A/C was on for ALL of the other tanks too, BTW) on I got 16.93 mpg, with no change in driving style.

What does this car do when the intake air temperature goes up? Is it pulling timing back? To drop 5 MPG simply because the ambient air temp has gone from 90 to 105 is fairly ridiculous. Fifteen degrees shouldn't make that much of a difference to the engine's systems. On the way over last Sunday to LA, through 109 degree temps, the car recorded 16.7 MPG so this isn't a statistical abberation.

Also, the mileage doesn't seem to change until AFTER the car is shut off and restarted in the desert heat. It's like the computer checks the ambient air temp at start up, then assumes that's where the setting remains for the rest of that key-on cycle.

My kingdom for a plug-in, real-time data analyzer!
Eric

19mpg city after 35,000 miles on her!

I havent actually calculated the MPG, I just pay attention to how many miles I fill up at..... And usually its well after the light comes on, the needle practically is on the line. I think when I look at the slip its usually around 13.4-13.7 gallons? That sound right?

I usually get 200 miles to a tank, driving 15min to work, all city and the lights are close.

I had a friend who just had a lung transplant up at Seattle, (hes doing great), so I drive from Portland to Seattle, and get well over 300 miles to the tank.

So I started driving like a sissy, shifting around 3500 or less.... its painful, but i got about 250 to the tank.

Wasnt worth it to me, I enjoy driving like every light is a race to the speed limit :D. That and I love hearing my wife say "Do you have to drive that fast". Why yes honey, I do :).

I think one thing to think about too. A lot of people see 1.3L and expect that kind of mileage. But we have 3 combustions per RPM vs a piston. So its more like a 3.9L. Maybe my logic is bad there.

I don't have any fancy spreadsheets able to post atm but figured I'd chime in here as well.

I've a 2005 MT RX8, purchased Feb 05. (White) I live in South Florida and use the car mostly for commuting to/from work (23miles each way). It sees full highway speeds on occasion, about 1x per month.

I've tracked every single fillup since I owned the car (thanks to a nifty Smart-List-To-Go database I wrote for my Palm).

I've now exactly 69 fillups recorded, over the spam of 16.7k miles on the car.
I'd estimate about 85% were from the same Station, and about 90% were complete fillups (over 12 gallons, I'm one of those who relies on the light before I stop).

My average MPG have actually been slowly increasing since day 1... I started at about 17.0 and it's been steadily climbing to now at 18.1mpg. The highest I've ever gotten on a full tank was 20.8, and the lowest was 14.2 (one very odd fillup, average lowest was around 16ish).

Average distance between fillups has been about 230-250 miles. Worst was 191 and best was 271.

Not the greatest gas milage in the world, but then again my previous car ('93 Eagle Talon, only got about 23-24 in the same town). I'd drive this car over my Eagle any day :)

Well some are saying that the new engine flash post recall work is affecting mileage a bit. Itll be interesting to see.

I got the flash a few weeks ago. I thought that it would be worse for gas mileage. But..... I am getting 10 miles per tank more than before the flash. I drive the same route to and from work everyday and have made no side trips.

They did replace 2 of the three plugs (odd?) at the same time. I found this odd since i just had all the plugs replaced 3000 mile ago with the "new plugs", and could not figure out why only 2 would be replaced.

Do you think the plugs wear that fast, and do new plugs make that much of a diference after so few miles?

Not that is means anything other than what I observed, a few months after I got my car I had to go in to get the plugs changed since the "new" plugs had been on backorder and so they weren't available when I picked up my car and had to wait for them to come in. They were replaced with the previous type of plugs at time of delivery. Well, the first full tank of gas with the new plugs I got 25.62 mpg with my same route and everything where I usually got an average of 23. Of course, it then promptly settled back down into my average range so I don't know that the plugs caused this to happen. Probably just dumb luck. :)

My mileage seems to have got worse with the recall work. I did 70 miles of highway at 70-75MPH with gentle acceleration and got 20.5MPG. I think I was doing at least 22-23 before.

Wish I was getting better and not worse.

I'd like to see one comparing MPG vs RPM.

Range 4 to 5K
Range 5 to 7K

for those drivers that use this range consistently. I just got 10.3 MPG it was in the 6 to 8k range, and alot near 8k.

Funny thing normal driving varies greatly, but I can get 20 plus on the freeway.

I have a AT, and I drive in the range of 5k - 7k 75% of my miles. I get 18mpg. I red line it once a day or more.

Well have driven my car painful genitally in the past and got no better then 13mpg city. Driving normally I get 12 to 12.5 mpg. Rotary God said that he could get 18mpg city in any RX-8 by shifting at 3K rpm I disagreed but figured I should give it a try. So for 10 agonizing days I drove 97% of the time below 3k and the results were 13.6 mpg and Mazda still says the car is working fine.

Loved the RX but I hate Mazda and their "who gives a shit" attitude!

I belive some cars are cursed with unusualy bad Gas Millage. I agree with Rotary God that any car capable of gettin 18mpg can get that driving in the city. Some cars like yours, cant obtain that so its worthless to try.

I wish the reason that some cars dont get more then 12/13mpg was discovered though.

I wish the reason that some cars dont get more then 12/13mpg was discovered though.

Here in lies the problem.

It is obvious to all that a select group of RX-8 have a problem that Mazda has chosen to ignore. It is decisions like this that earn them a place at the bottom of all car manufacturer for servicing their vehicles as reported by JC Power. It also costs them in bad PR and lost sales. I myself will slam this car and Mazda in this respect every chance I get to anyone considering a Mazda. I have decided not to get a C7 because of this poor support. I have had a hand in swaying other to choose a different car manufacture after relaying my problem.

What it would cost Mazda to just analysis and fix my car they have lost 10 times over in lost sales that I have been a contributing factor yet they sit in there offices wondering why they are rated so poor and what they can do to correct this. Fix your damn cars, stand behind your product.

Love the RX but MAZDA SUCKS!!!!!

Well telling us here doesnt do any good does it? Not buying a C7 doesnt hurt Mazda if they dont know you were going to buy it.

Complain to mazda, not to us.

Well telling us here doesnt do any good does it? Not buying a C7 doesnt hurt Mazda if they dont know you were going to buy it.

Complain to mazda, not to us.

My friend, you don't know that Mazda monitors this board???

This board not only tells Mazda but it airs their dirty laundry to their client base. I'll share something with you, when your screwing something up as a corporation the last people you want to know this are your potential clients. I can think of few more effective ways of telling Mazda then posting on this board and unlike a letter, once this is posted it can haunt them for years to come.

You think complaining about it here for the..... 100th time will change their minds. Im sure a Mazda PR looks at a lot of sites. Why dont you send them a personal letter to let them know you want a serious answer.

You think complaining about it here for the..... 100th time will change their minds. Im sure a Mazda PR looks at a lot of sites. Why dont you send them a personal letter to let them know you want a serious answer.

Actually I know it can. Zoom 44 once pointed out that several issues raised on this board had a direct effect on Mazda. Your idea of a letter is good if not one dimensional, rest assured that I am pursuing this on several fronts.

Your calling my idea one dimensional? Its not an idea its the best way to get anything done. Email is still a very unformal way of communication.

Here in lies the problem.

It is obvious to all that a select group of RX-8 have a problem that Mazda has chosen to ignore. It is decisions like this that earn them a place at the bottom of all car manufacturer for servicing their vehicles as reported by JC Power. It also costs them in bad PR and lost sales. I myself will slam this car and Mazda in this respect every chance I get to anyone considering a Mazda. I have decided not to get a C7 because of this poor support. I have had a hand in swaying other to choose a different car manufacture after relaying my problem.

What it would cost Mazda to just analysis and fix my car they have lost 10 times over in lost sales that I have been a contributing factor yet they sit in there offices wondering why they are rated so poor and what they can do to correct this. Fix your damn cars, stand behind your product.

Love the RX but MAZDA SUCKS!!!!!


:crying: :crying: :crying:

I fell sorry for those who bought this for city driving.

Plain and simple this is not a city car. :mad:

:crying: :crying: :crying:

I fell sorry for those who bought this for city driving.

Plain and simple this is not a city car. :mad:

I guess I missed that in the advertising. :Freak_ani

I went 70MPH highway for about 76 miles and only got 21.3MPG. Yep, post recall has lowered my highway MPH. :(

I went 70MPH highway for about 76 miles and only got 21.3MPG. Yep, post recall has lowered my highway MPH. :(
How did you determine this? Top off your car, drive for 76miles, and then top off again with 3-ish gallons?

In LA traffic and cruising up the 101 freeway north to Pismo Beach, I got 21.24 MPG. Coming back down the 101 and through LA, including getting stuck in the I-91 traffic for an hour, I got 21.9 (all the way out to Palm Springs)! The very next tank, cruising across the desert heat, with the A/C (A/C was on for ALL of the other tanks too, BTW) on I got 16.93 mpg, with no change in driving style.

What does this car do when the intake air temperature goes up? Is it pulling timing back? To drop 5 MPG simply because the ambient air temp has gone from 90 to 105 is fairly ridiculous. Fifteen degrees shouldn't make that much of a difference to the engine's systems. On the way over last Sunday to LA, through 109 degree temps, the car recorded 16.7 MPG so this isn't a statistical abberation.
As a follow-up post to my own post, I have to note that the high desert temps have fallen off to winter-time 60's, 70's, and 80's out there AND, contrary to what I expected, gas mileage across the desert did not improve. This I fear rules out external temps as a primary cause.

Pre-mix DID appear to net 1/2 a mile per gallon better average during both the "poor" portion and the "good" portions of my trips. I've now had the emissions recall performed and the car is FANTASTIC in the mid-range RPM! Before, I could do 70 mph and get 17 miles per gallon, or I could do 90-95 and get 18.5. Across the same section of desert. I attribute that to the lack of proper cylinder oiling at lower rpm and light throttle. The OMP settings change at different higher rpm, and driving in that range yielded better fuel economy.

In talking to a few others on here it was mentioned that there's a "cat preservation mode" where the ECM sends the A/F ratio plumeting from 14:1 down to 10:1 when cruising above 4100 RPM for more than 15 seconds at a time (without moving the gas pedal). Since my desert cruise does just that (though at a slightly lower RPM), this is what I think is happening. On some cars, the ECM is seeing a condition it thinks needs "Cat Preservation Mode" and jumps to it, essentially removing the O2 sensor controls and running very rich. In LA traffic, hills, and turns, the ECM never sees the 15-second tripwire, and so runs happly lean the entire time. Just try to do a constant speed in LA traffic for any length of time! With the off-throttle coasting down hills in LA, the fuel economy picks up into the 20s, with the highest so far being nearly 22.

Taking this thought into account, on my last trip to LA I spent time off the cruise control lifting my foot off the gas slightly every so often. I averaged 19.5 on the way out. On the way back, with the new tune, and driving with the cruise set for a comfortable 82 mph, I averaged 19.2, with 5 blasts up to the range of 120 mph or so! Now I just need to cool my hot foot down and see what this tune will produce when lightly cruising the entire way across the desert. Hopefully, on the way to Sevenstock this coming weekend!
Eric

How did you determine this? Top off your car, drive for 76miles, and then top off again with 3-ish gallons?
Yep. Filled up before I got on the freeway and when I got to my destination I filled up. The gas stations are on the way to/from where I traveling. It was a MPG test to see what I would get.

posted for future reference by me:

I drove from NJ to OH and back in the 8.
I would say it was between 80-85 degrees on both drive days, sunny, and no traffic. This was in late July.

Mileage on Tripmeter/gal/$$/mpg
000/12.543/40.50/19.294*
178/.874/28.92/20.059
366/8.962/29.09/20.978
611/13.10/41.92/18.702**
642/2.709/8.40/11.443***
890/11.819/38.52/20.98
1183.7/13.0/42.00/22.592****
*reset meter at 242 to begin trip
**got to location so includes some local driving
***a very spirited cruise through some farm country in the middle of nowhere
****personal record

With the exception of the cruise, I did most of this with the A/C on low and windows up. On the rare occasions when I find a suitable place to have some fun, I usually drive with the windows down to better hear whats going on.

The 11.4 is also a personal record of sorts. I might be able to get into single digits at an autocross.

Yep. Filled up before I got on the freeway and when I got to my destination I filled up. The gas stations are on the way to/from where I traveling. It was a MPG test to see what I would get.
The reason I asked was that such a small amount of fuel added to fill the tank can introduce a HUGE error in the mpg calculation. Not that your observed mileage is remarkable either way (though a bit on the low side from MY experience), but the level you "fill" to changes from tank to tank and a 3gal top-off isn't a good way to measure your mileage. With a 3gal fill, the difference of only a pint either way can change your calculated mileage by 1mpg.

Then again, for all I know, you filled it until fuel was running down the side of the car on both occasions, just to be sure. :)

The 11.4 is also a personal record of sorts. I might be able to get into single digits at an autocross.
...and I think this is an example of what I'm talking about. It appears this record low mpg for maxx is calculated from a fillup that was only 2.7gals.

Again, I'm not debating that these low-volume top-offs ABSOLUTELY are off by huge amounts, but the possibility certainly exists.

As much as I love my 8, poor gas mileage is putting a damper on my enjoyment. Having owned an 85 RX7 for 10 yrs, I absent-mindedly bought the 8 after ditching a 2001 Jeep Cherokee this summer due to poor gas mileage as a commuter downtown to work. I did compare posted gas mileage for my old RX7, Jeep and 04 MPV as folows:

AUTOMOBILE PUBLISHED MPG
CITY / HWY/ COMBINED
MAZDA CANADA -RX8 - 18.4/ 25.6/-
US DEPT. ENERGY-RX8 - 18/ 24.0/ 20
MAZDA CANADA-MPV - 18/ 25.0/ 20
US DEPT. ENER-JEEP 2WD - 16/ 21.0/ 18
US DEPT. ENERGY-RX7 - 17/ 24.0/ 20

Well, the fact that it was better than the Jeep was all it took and since it was potentially better than all the others too was a bonus......well, I've only mannaged to record 7 fill ups since acquiring it in August but considering I drive 60 km a day with at least 80% hwy, it isn't as good as the numbers posted above. After the flash it seems to have dropped another 10-15% which really sucks.

L/100km/ Diff. City/ Diff. HWY/ MPG/ MPG(US)
12.8/ 0%/ 39%/ 22.0/ 18.3
13.2/ 3%/ 44%/ 21.3/ 17.8
13.7/ 7%/ 49%/ 20.6/ 17.2
13.6/ 7%/ 48%/ 20.7/ 17.2
15.4/ 20%/ 68%/ 18.3/ 15.3
14.2/ 11%/ 55%/ 19.8/ 16.5
16.1/ 25%/ 75%/ 17.6/ 14.6


What you see above shows a drop in the last 4 fill up after the flash(in bold). When compared to Mazda's posted mileage for city and hwy, it used to vary between 0-7% and 39-49% respectively. Now it's as much as 25% compared to city and 75% compared to hwy. I figure with 80% hwy I'm somewhere around 40-50% off the mark. Personally I think this is way to far from published..it's criminal!

The reason I asked was that such a small amount of fuel added to fill the tank can introduce a HUGE error in the mpg calculation. Not that your observed mileage is remarkable either way (though a bit on the low side from MY experience), but the level you "fill" to changes from tank to tank and a 3gal top-off isn't a good way to measure your mileage. With a 3gal fill, the difference of only a pint either way can change your calculated mileage by 1mpg.

Then again, for all I know, you filled it until fuel was running down the side of the car on both occasions, just to be sure. :)
Well I have a longer highway trip coming up, so I'll see later this week.

I do notice that the RX8 fuel tank design easily tops off quick and spills down the side of the car. You learn to basically end fueling at the first click off of the pump handle.

What you see above shows a drop in the last 4 fill up after the flash(in bold). When compared to Mazda's posted mileage for city and hwy, it used to vary between 0-7% and 39-49% respectively. Now it's as much as 25% compared to city and 75% compared to hwy. I figure with 80% hwy I'm somewhere around 40-50% off the mark. Personally I think this is way to far from published..it's criminal!
I think my mileage has dropped post recall work as I've stated before. It is amazing that some people have had MPG increases. Wish I was one of those folks.

I've seen a drop of 2 MPG on the highway, which is about 10%.

I do notice that the RX8 fuel tank design easily tops off quick and spills down the side of the car. You learn to basically end fueling at the first click off of the pump handle.
My experience with this car over the last 8mos has shown that it also depends upon WHERE you top off. Sometimes it will take very little after the pump clicks off, and in some places it'll take an extra 3/4 gallon. I wish I'd paid closer attention to when/where/how this happens... I've taken fuel in at least a dozen states and I wonder if there's any consistency on that basis, mostly in the states that have those accordion -shaped "collars" on the pumps. Never mind the reality that you can't even be "in charge" of your top-off in NJ because they won't let you pump it yourself (I know NJ isn't the only state like that but I can't think of the others).

My experience with this car over the last 8mos has shown that it also depends upon WHERE you top off. Sometimes it will take very little after the pump clicks off, and in some places it'll take an extra 3/4 gallon. I wish I'd paid closer attention to when/where/how this happens... I've taken fuel in at least a dozen states and I wonder if there's any consistency on that basis, mostly in the states that have those accordion -shaped "collars" on the pumps. Never mind the reality that you can't even be "in charge" of your top-off in NJ because they won't let you pump it yourself (I know NJ isn't the only state like that but I can't think of the others).
I'm just constantly wary now of getting petrol down the side of the car.

Oregon is another state I believe.

It all depends on the sensitivity of the pump. Some are more sensitive, some less.

One funny experience... At one place with "those accordion-shaped collars on the pumps," when it was full and clicked off, it jiggled the handle enough that it suddenly popped out of the hole and onto the ground. It kinda looked like the 8 said "Okay, I'm full... paTOOEY!" :D:

Well I have a longer highway trip coming up, so I'll see later this week.

I do notice that the RX8 fuel tank design easily tops off quick and spills down the side of the car. You learn to basically end fueling at the first click off of the pump handle.I never tried to top off the 8. I always stop when the pump stops, thinking that they stop about the same range... but it's true, some pumps stop really close to full and some have that extra half-gal to go. This is probably skewing my readings a little.

(Although, if you go to the same exact pump and stop at the first click--then that should be consistent.)

I was tempted to top it off, but I don't want to spill gas down the side of my car.

I've done that once in my Mazda Protege .. not fun.


If you want to go for the extreme top-off, if you run the pump at very low speed (barely depressing a handle), the auto-shut-off occurs a lot later, and I was able to squeeze out the absolute max that way back in the day, to the point where I overflowed my Protege's tank.

Most all of my mileage estimates have been over runs of 130 miles or more. I'm fortunate enough to do most of my work from home, so "commuting" to me means zipping out to LA to photograph some cars, then zipping back home.

It looks like I'll be hooking up with the "Desert Caravan" to Sevenstock when they pass through my town on Friday. I'll be extremely interested in everyone's mileage crossing the rest of the desert into Palm Springs. This would be a good time to see if 33 RX-8s, all cruising at the same speed during the same atmospheric conditions on the same road can reproduce the fuel economy I'm seeing aross this stretch of desolate countryside.

It kinda looked like the 8 said "Okay, I'm full... paTOOEY!" :D:
Heh heh... Sounds like a scene from the movie "Cars".

Great work Norton! I thought that i just had a leak in my fuel tank but it would appear that i am not alone!!

I have heard that cruising at about 4000 rpm is optimum for fuel economy when cruising around - Does anyone know if there is any truth to this?

I have just gotten the recall flash so I updated my spreadsheet and came up with the following MPG numbers until this point:

July 2003 Port Flash - 6,567 miles 14.9 MPG

M Flash - 8,375 miles 16.4 MPG

R Flash - 6,955 miles 16.5 MPG

I do mostly in-town driving and I drive in a spirited fashion. My car is totally stock.

Chart format gets lost when posting but here is the total history of my 06 fuel use. Pretty consistent with an average just over 19mpg. I have a heavy foot and use it.

Purchase,Date Price,($/G),Gallons Purchased,TotalCost, Odometer(miles) Station, FilledTank?, MPG
8/7/2007 2.889 13.155 $38.00 4,924 Kangaroo Y -
7/31/2007 2.999 13.341 $40.01 4,683 Citgo Y 18.32
7/23/2007 3.079 13.805 $42.51 4,438 Citgo Y 18.36
7/22/2007 3.109 10.937 $34.00 4,134 Citgo Y 22.02
7/15/2007 3.039 13.737 $41.75 3,928 RaceTrac Y 18.84
7/8/2007 3.119 12.665 $39.50 3,646 Citgo Y 20.53
6/28/2007 3.169 13.096 $41.50 3,385 Citgo Y 20.61
6/9/2007 3.249 12.927 $42.00 3,141 Citgo Y 18.63
5/29/2007 3.279 13.570 $44.50 2,904 Citgo Y 18.33
5/20/2007 3.229 12.545 $40.51 2,662 RaceWay Y 17.83
5/15/2007 3.189 13.012 $41.50 2,401 Citgo Y 20.81
5/10/2007 3.069 13.362 $41.01 2,145 Kangaroo Y 19.67
4/27/2007 3.139 13.857 $43.50 1,897 Citgo Y 18.56
4/19/2007 3.099 12.584 $39.00 1,649 Citgo Y 17.90
4/14/2007 3.239 11.964 $38.75 1,393 Shell Y 20.34
4/9/2007 2.999 13.188 $39.55 1,161 Citgo Y 19.39
3/31/2007 2.699 13.763 $37.15 915 Hess Y 18.65
3/28/2007 2.729 12.825 $35.00 622 Kangaroo Y 21.29
3/26/2007 2.719 12.871 $35.00 379 Shell Y 18.95
3/22/2007 2.629 12.933 $34.00 144 Crown Y 18.26

Total Quantity Purchased (Gallons) Total Cost ($) Average Price ($/G) Average FuelEconomy (MPG) Total Fill-ups 260.137 $788.72 3.034 19.33 20 http://www.northcarolinagasprices.com/images/msg.gif

:banghead: My first measured fuel tank milage is ONLY 14.3. I realize that 95% was city and it was hard (Just picked up my used 2004) but this seems low. It have been hot mid 90's. Any thoughts?

I have an 04 I just picked up in July. If I do mostly city w/air I got 15mpg. If I don't use the air and do 50/50 city and highway I get 20. On highway only I get 23 or better.

ok so i bought an 06 Shinka, and took it on a rather long road trip this last weekend. what i have seen is that the hotter the temp the worst the gas mileage. i went from Corona Ca to Durango Co. and from the AZ border to the NM and CO border i was getting average 24.5 mpg. with a few fill ups at the 27 mpg mark. i broke the 300 miles per tank a few times. but as soon as i was on my way home in the heat. it went to 19-21 mpg.
most of the highway driving was at 90+ in 6th gear. so that is what 4750 rpm. or there abouts. so the comment about running rich for over 4500 rpm over long runs i would say is wrong. although the temp makes sence to me. or it's the sh*ty gas i got in CA.
i now have just over 10K miles on mine. bought it with 7800. and used 1/4 quart of oil.
happy trails and keep er safe.

HR

chavy85, Consider yourself lucky. After 88k miles, my 08/03 build only once got 24.5 on an unusual string of consecutive 65mph runs. Based on the conditions you describe, my mileage would be about 17-22 rather than your 19-27. Although I've applied all of the ECU patches and followed most MPG discussions (note my handle) from the beginning, I don't recall any significant design mods that Mazda has announced that would make up the difference in what you (and what seems to be most '06s and beyond) and my old build models make for MPG. MPG aside, you won't find a finer handling marque, especially at the limits!

Anyone, Have I missed something that would boost my MPG by a mile or two? Not that it matters much to me, other than due to design curiosity, as I now drive an '06 Prius and only take the '8 out for track days. Once you've driven a true hybrid, it just seems pointless for a daily driver to not recover energy during braking or go electric only, in jammed/slow traffic. Plus, you can't deny Toyota/Denso's win out of the box in their first 24 hour endurance run with a capacitor hybrid prototype. Makes the Audi LeMans diesels look like pikers. Read the writing on the wall.

hmm..I've been getting about 250 miles with 13.5gal of gas.
that's about 18.5-19miles per gallon.

It would be nice to get about 22-24miles per gallon like my evo did
but I am not complaining.

BTW, I have a pretty heavy right foot so I am not granny driving my car.

I just bought the car about 2 weeks ago with 10k miles on it.
It's a 6spd GT.
I just went to mazda to have some TSB's and was told that it had a new motor
put in @ 6500 mark.

Im really hoping I don't have any future probs with this car.

hmm..I've been getting about 250 miles with 13.5gal of gas.
that's about 18.5-19miles per gallon.

It would be nice to get about 22-24miles per gallon like my evo did
but I am not complaining.

BTW, I have a pretty heavy right foot so I am not granny driving my car.

I just bought the car about 2 weeks ago with 10k miles on it.
It's a 6spd GT.
I just went to mazda to have some TSB's and was told that it had a new motor
put in @ 6500 mark.

Im really hoping I don't have any future probs with this car.

thats not good if u didnt know that it had a motor replacement...

well...when I ran carfax before purchasing the car nothing came up.

Why is it bad that the car had a new motor put on?
The car drives absolutely fine though.

At first, I reported to this thread (last year) I was getting 18mpg @ 70% hwy (aggressive)


Now, after 15k miles, I am getting around 20mpg @20% hwy miles (moved) (aggressive).

20MPG
But a month ago I was getting only 16. And that's because this car was staying in garage for a couple of month.

Alright, so after a highway trip, here is what I was getting:

70mph avg (hilly 4k-7k elevation) 24.5 mpg (full tank) 90% highway
90mph avg (same as above) 23 mpg (3/4 tank) 100% higway

Kind of surprised everyone complains about gas mileage on these cars. I drive mostly back roads with some city and in the last two weeks have gotten between 21.5 to 24.5 mpg. Just driving normally.

I have owned the car about 2 1/2 months. I average between 13.8 to 14.3 MPG. I do 95% off HWY driving but the higher numbers did have 30% HWY miles. I do have a big right foot, but I am having trouble beliving the RX8 getting WORSE MPG than my 318HP/380lb.ft. 4000lb Audi A6. I drive both the same way. I get 16-17 in city and 24 on the HWY in the Audi. Granted the RX8 is much more fun to drive but the A6 is much faster. Does anyone else get this bad of milage?

there is a recall on the plugs and some other things you shoudl get done. then you MPG should go up. mine did.
went from 18-19 to 23-25 best ever was 27.
new plugs and recalled cat was my problem.

HR.

Filled up went to local grocery store, 3 miles
Drove 234.7 miles. Mostly doing 57-59mph. North 45 to Madisonville.
Slowest 49mp, fastest 64
One bumper to bumper stretch- burning van on freeway.
Hit 81mph but only briefly.
So what's my average mpg? 25.81mpg?
9.093 gal reg unleaded @$2.529/ga = 23 bucks !l

Oh yea, everyone passed me, including a one legged duck!

Dealer replaced 2 leading plugs / emissions recall 4206F yesterday

dAMN the most i can get out of a full tank of 91 is like 250 miles and thats with the low fuel light on for quite a while. my car has 54k on it and its a manual i might change the spark plugs this weekend which i think should help out a little

there is a recall on the plugs and some other things you shoudl get done. then you MPG should go up. mine did.
went from 18-19 to 23-25 best ever was 27.
new plugs and recalled cat was my problem.

HR.

I made a appointment with a different dealer for service. I told them the crappy gas milage I had and they told me that was TYPICAL!? So then I told them about my high rpm power loss. They are going to look at it as well as a couple of other things. I will ask them about the following:

Coils
Plugs
Cat

All the othe PCM updates have been done. I really don't think my MPG should never get above 14.3.

Is their anything else I should have them check?
Thanks everyone:rolleyes:

[QUOTE=psonoda;2113316]>>>>>>>>>> I really don't think my MPG should never get above 14.3.

Pardon my English but you say>>> should never get above 14.3
Do you mean.... below?

What bad english. I meant to say my MPG has never been above 14.3. It typically ranges between 13.8 to 14.3. Very Bad!

I took it to the dealer yesterday. They told me the MPG might improve if I changed the plugs. A dealer cost of $240. Ouch.

Interesingly enough the problem I reported to Jake Sweeney Mazda about the cluch engaging funny came back with "No problem found" However, Kings Mazda was able to find and replace two broken motor mounts. The car is feeling much better as a result.

I bought plugs from Napa for just under $100 for the set. (Dealer wants $160) Plan to replace them this weekend. Will let everyone know if there is a milage change.

ok understand. Yikes, that's too low. Guess spark plugs change will help it. How long has your 8 had its plugs?miles wise

I drive my 05, RX-8(SE3P Auto 4 Speed) in Dhaka, Bangladesh, where temperature is around 35 degree celcius and in city driving I get around 4 kilometer per litre with 92 Octane.

Can someone tell me why do I get a horrible fuel consumption?

Thanks.

I was getting a consistant 13-14mpg on my original engine. Seems to be close to the same with my reman one so far, but I figure I ought to wait for it to be broken in before I worry.
I do 70 city / 30 highway and drive moderately.

New 07 RX-8 MT here, the past 3 months I average 18mpg if I drive very very conservately, 16mpg if I romp throughout full throttle 7000-9000rpm during the trips.

I just finished chaning my spark plugs. I thought is was going to be a real pain until I realized there was easy access through the driver's wheel well.

By jacking up the car and removing the front wheel, I had almost a straight shot to the plugs.

http://www.audiogearlab.com/rx8/images/Spark-Plug-1.jpg

http://www.audiogearlab.com/rx8/images/Spark-Plug-2.jpg

http://www.audiogearlab.com/rx8/images/Spark-Plug-3.jpg

http://www.audiogearlab.com/rx8/images/Spark-Plug-4.jpg


As you can see the plugs were somewhat dirty. If you change your spark plugs, I recommend you have lots of extensions. It made the job much easier.

Another thing I found was the the forward leading spark plug boot was loose while the rear trailing plug boot was nearly off. I had to pinch the boots to get good contact between the boots and the spark plugs. I will let you know about the milage with the next tank. Going to fill the gas up and test her out.

was that a minitab spreadsheet?


also use an 18" extension and a joint and its even easier!

My first tank after the spark plug change has improved my milage slightly. This tank I got 15.1 MPG. A small but welcome improvement.

I was wondering if anyone who has added an upgraded air box or air filter has noticed a MPG improvement? I was thinking about changing to a K&N filter while modding the factory airbox (Removing the internal baffles) and reducting the air out the front of the bumper for less restricted cooler air.

Any thoughts?:uhh:

I have changed my spark plug and changed the stock filter to K&N drop in filter. Now I get 10 MPG with 90% city driving.

damn... 10 mpg sucks.
have you checked your cat? the way you check them is drive the car till it's fully warmed up. then let it idle and jack it up. take a temp gun and check the temp on the front and the rear of the cat. the guns are rather cheep kinda like and infer red temp gauge. when checking have some one rev the engine a few times to get a good amount of exhaust flow. if the temp on the front is higher then the back of the cat then it's plugged. and needs to be replaced.
the back of the cat should be a lot hotter then the front. that means its doing it's job.

HR

psonoda What is the Gas saving kit? I've never head of it...

HR

damn... 10 mpg sucks.
have you checked your cat? the way you check them is drive the car till it's fully warmed up. then let it idle and jack it up. take a temp gun and check the temp on the front and the rear of the cat. the guns are rather cheep kinda like and infer red temp gauge. when checking have some one rev the engine a few times to get a good amount of exhaust flow. if the temp on the front is higher then the back of the cat then it's plugged. and needs to be replaced.
the back of the cat should be a lot hotter then the front. that means its doing it's job.

HR

I have never done it before. I will check my Cat within a few days and let you know the result. Thanks for the tips.

psonoda What is the Gas saving kit? I've never head of it...

HR

It is made of Aluminium and you have to fix it after the MAF sensor or before the throttle. You can see the description on ebay. I bought it for 10 bucks but now I took it off. It really does NOT work.

I've had my 07 for about a week with 2 refills and 60 highways & 40 city driving. First refill, 220 miles and 15 miles/gallon. Second refill, 255 miles 17 miles/gallon.

I'm content with 17miles per gallon. However, a friend with an RX7 told me gas mileage should improve as the rotary breaks in. Btw, I'm following Racing Beat's recommendation on "breaking in" he 8.

I'll re-post this again in the appropriate thread lol....

I'm not that good at converting mpg's, but I'm from Ontario, Canada, and up here in kms, I get about 330kms on a full tank from start to finish. I don't think I got it any higher than that, now God-willing, I plan to drive to the States this summer for vacation, so I hope to get more mileage than that. So, on average, the 330kms is about 50-60kms of driving a day, and I fill up every 4-5 days, at about $52-$54 a tank. I spend about $250-$300 on gas a month. Is that average for you guys, or is that good gas mileage? Also, at that rate, what's the mpg I'm getting?

The drive from London to Ottawa on highway 401 > 416 > 417 costs me $65-70 in gas, over 600 km. Don't know if that helps anyone but that's the deal.

The drive from London to Ottawa on highway 401 > 416 > 417 costs me $65-70 in gas, over 600 km. Don't know if that helps anyone but that's the deal.

Wow, how does that work? Unless the gas prices are cheap, cuz to fill a tank it costs about $55.00, and if you do only highway kms, you could probably get 400 kms!

Interesting info, I actually am getting pretty decent mpg

Do they talk about MPG on the Z, Mustang and Corvette pages? My wife has an Armada. I was once asked, "Wow that thing must get awful mpg?!? huh?"

I simply responded, I had no idea, I'd never measured it. Why bother?

It's a sports car. If you want mpg buy a Prius not an rx-8.

Here's the Prius g-tech 0-60 run, enjoy.
http://priuschat.com/forums/attachments/prius-technical-discussion/8235d1206416768-prius-0-60-fun-gtech-runs.jpg

Toyota Prius sedan - hybrid 1.5L gasoline + electric

0 - 60 Time (seconds) 1/4 Mile Time (seconds) 1/4 Mile Speed (mph) Braking 60 - 0 mph (ft.)
11.43 18.54 78.00 137

Sexy ...
http://fp.images.autos.msn.com/merismus/YearGlance/y443618a.jpg

Jeff Dunham on his Prius and how he loves it.
http://www.youtube.com/watch?v=GQcSOP2AzXU

Meh

MPG on a rocket may seem pointless, but knowing your MPG can give a bit of insight on how your RX is performing. Especially if you are on a constant mental note, while breaking the speed limit. I know that after an oil change MPG gets a bit better (at best maybe a 1.1 mpg addition) and I acceleration increases. After seeing psonoda plug change; I'm beginning to wonder if that may be a reason for my gradual decrease in adrenaline/acceleration. To me; being throttled into my seat is why I have an RX, but noticing those little things lets me leave my body print a bit longer in the cockpit as well as knowing when it's time to crack the hood. So kudos to those that watch the MPG. I now know when my fuel injectors kick in and when to clean them because of these guys.

Meh

MPG on a rocket may seem pointless, but knowing your MPG can give a bit of insight on how your RX is performing. Especially if you are on a constant mental note, while breaking the speed limit. I know that after an oil change MPG gets a bit better (at best maybe a 1.1 mpg addition) and I acceleration increases. After seeing psonoda plug change; I'm beginning to wonder if that may be a reason for my gradual decrease in adrenaline/acceleration. To me; being throttled into my seat is why I have an RX, but noticing those little things lets me leave my body print a bit longer in the cockpit as well as knowing when it's time to crack the hood. So kudos to those that watch the MPG. I now know when my fuel injectors kick in and when to clean them because of these guys.

this is so true :bowdown:

Short story...(im bored)
so I parked my car next to a Toyota Sequoia, and a woman that was approaching her SUV asks me how much mpg I get on my 8, and I say 17, and she goes
"OH MY GOD!!!" with her jaws wide open, so I shrug it off saying "hey its a sports car:)". apperantly she thought my car was a steriotypical import compact with crazy mpgs.

Anyways I get 17.5mpg solid right now @ 4000miles, one thing that I realized is that I get the same mpg regardless of grannying it for the entire week or spiriting it the entire week.
It seems like its pumping way more gas at lower rpm(2-3k) than at higher rpms since you got a whole lot of load to push the car with smaller gears and lower rpms. and maybe I'm wrong.

just wanted to add how difficult it is to find a econo 4 bangers right now. I've been searching around for a while and I dont see any oldie civics for under 1k:( the cheapest one starts at 2.5k with 220k miles. I remember looking for my first car just a couple of years ago, where you had alot of choices for under 1k.

I have now just averaged 22 mpg on each of three consecutive tanks.

13.5 gallons each time, marked to a T. Range was 301.7, 292.4 and 297.3, respectively.

I waited until the 3rd tank to post this.

I think the key is to shift around the 3k mark, obviously avoid idling, and stay under anything over 4k on the highway if maximizing fuel economy is your goal.

Also, make sure you redline it at least once a day, even when you're trying to save fuel. It's preventative maintenance.

I have now just averaged 22 mpg on each of three consecutive tanks.

13.5 gallons each time, marked to a T. Range was 301.7, 292.4 and 297.3, respectively.

I waited until the 3rd tank to post this.

I think the key is to shift around the 3k mark, obviously avoid idling, and stay under anything over 4k on the highway if maximizing fuel economy is your goal.

Also, make sure you redline it at least once a day, even when you're trying to save fuel. It's preventative maintenance.

I think I got that one covered..... as for the whole "under 4000" thing..... yeah.... <shrugs> I'm surprised I haven't gotten any tickets yet :P

PS- I get about 16-19 mpg, and I lean more to the spirited side of driving my 8.... assuming a) I'm not on post (army) or b) traffic permits... don't try to kill people when I go out, but if ya are driving too slow, in the left lane, I won't make you move, I'll just go around you...

I just gave up my 04 GT. Mostly because of some near-death experiences :uhh: this past winter despite Blizzak LM-22s. I used to park it if the weather was bad, but changed jobs and now need to drive everyday.

As for mileage, my 27,000 miles over 4 years averaged 13.4 MPG. I would say that it was 25% highway. Winter was a killer.

Replaced it with a 08 STI, a different car. Far less stares and oogles, and heavier handling, but the torque and my chances of living another year are higher!
Bye!
:Eyecrazy:

I'm getting a consistent 14 -14.5 mpg. I almost never shift below 6K RPM, and redline wheneverthehellIfeellikeit. (In other words: very aggressive.)

My solution was to buy a Honda Fit for my "everyday" car. It's the best little econobox car on the market. It's moderately fun to drive. I've gotten 28.5 mpg (70% city) on the first two tanks, with that same lead foot that drives the 8. (The results of the lead foot aren't quite the same, but it's fun trying.)

Without the Fit, I would not appreciate my 8, or drive it like the sportscar that it is. With it, I can keep the 8 clean, dry, polished, garaged, gassed, pretty, and drive it on my terms, not worrying about the gas mileage.

note to whoever ran this regression, i just took a look at it, and for driving style it seems as if you are trying to introduce an indicator variable into the regression. however you are using the same variable and using 1, 2, 3, etc to indicate different driving styles

this cannot be done because it inbeds a set scaling between the styles

you need to introduce n-1 indicator variables, where n is the number of driving styles and the indicator variable CAN ONLY BE 0 or 1

sorry i took a few courses on advanced regression models and i just wanna help

if whoever ran this regression is still interested in revising it PM me!

note to whoever ran this regression, i just took a look at it, and for driving style it seems as if you are trying to introduce an indicator variable into the regression. however you are using the same variable and using 1, 2, 3, etc to indicate different driving styles

this cannot be done because it inbeds a set scaling between the styles

you need to introduce n-1 indicator variables, where n is the number of driving styles and the indicator variable CAN ONLY BE 0 or 1

sorry i took a few courses on advanced regression models and i just wanna help

if whoever ran this regression is still interested in revising it PM me!

HUH?:dunno: I am looking for my slide rule now.

I must reiterate - city mileage on this car is TERRIBLE!

So I was driving a fair bit around town lately and noticed my gas gauge just plummet. I filled up and drove around town for 50 miles or so (chores :)). This is in NYC. At the end of the day I went back to the pump to fill up and I had consumed 4.3 gallons in those 50 miles. Works out to 11.6mpg.

:(

It has been a while since I posted in this thread. I have been keeping serious records of this for some time now. Let me know what you think.

http://www.rx8club.com/attachment.php?attachmentid=124281&stc=1&d=1217527930

The last entry was 100% freeway driving between 80-90 MPH and heavy on the brake and gas. From 6/21 on was with the new engine installed. The MPG on the 6/21 was combo city and hwy driving keeping the revs under 4k.

My mpg observations:

1. Since I got the last TSB in may, my mpg went up from about 21.5 to 22.5 per gallon -- I can get to 300 miles before the light comes on every time.

2. The RX8 is indeed much worse in city driving than on the freeway. I never take the 8 on short trips. Translation, going fast (i.e >65) may reduce your mileage a little, but going slow (< 40) will reduce it a lot.

3. My cousin's wife had a Mini Cooper S. After she had it for a couple of year or two, my cousin took a ride with her and noted that she never used fifth or six gear. After he pointed it out, she said "Yeah, I never use those". I also had a self-proclaimed muscle car afficianado who had never driven an MT ask me if I had ever gotten into sixth gear, with the implication being that if I'm in sixth gear I must be going really fast. So, I wonder, do all the RX8 owners getting < 15 mpg understand that you get better gas mileage in higher gears?

my current vehicle (2004 expedition) gets epa 14 city, 18 highway

and i've proven this wrong soooooo many times, my best average on a tank was 25 mpg (i tried for a while :P) 100% on the highway of course, but to achieve best highway mileage, go the fastest, using the least power. so don't go at a recomended speed, every car has its own sweet spot. for the expedition, it would be 65 mph, im on average about 1.5 revs for that whole time (i have a cvt transmission) as soon as i bump that 67 up to 80, my mpg shoots down to a wimpy 18. and why? DRAG resistant coefficient or w/e.....corvettes are epa'd at 26 highway, my friends can get them up to 35 almost 40 mpg, just for finding that sweet spot, best rpm to speed ratio.

for city, i can get up to 18. i know in the rx8 you get fuel cut off for downshifting, but what i do in the expedition, im technically a very conservative driver, i use my brakes as very little as possible, and i never ever come to a complete stop, judge how far i have to go, and idle the rest of the way to the stop light, by then it has already turned green, and i apply very little gas to get back up to my original speed.

just some tips for getting better gas mileage.

my current vehicle (2004 expedition) gets epa 14 city, 18 highway

and i've proven this wrong soooooo many times, my best average on a tank was 25 mpg (i tried for a while :P) 100% on the highway of course, but to achieve best highway mileage, go the fastest, using the least power. so don't go at a recomended speed, every car has its own sweet spot. for the expedition, it would be 65 mph, im on average about 1.5 revs for that whole time (i have a cvt transmission) as soon as i bump that 67 up to 80, my mpg shoots down to a wimpy 18. and why? DRAG resistant coefficient or w/e.....corvettes are epa'd at 26 highway, my friends can get them up to 35 almost 40 mpg, just for finding that sweet spot, best rpm to speed ratio.

for city, i can get up to 18. i know in the rx8 you get fuel cut off for downshifting, but what i do in the expedition, im technically a very conservative driver, i use my brakes as very little as possible, and i never ever come to a complete stop, judge how far i have to go, and idle the rest of the way to the stop light, by then it has already turned green, and i apply very little gas to get back up to my original speed.

just some tips for getting better gas mileage.


I'm pretty sure each car is listed with a drag coefficient, when I get some time, and I'm reviewing for my FE exam in April, I'll whip out my Fluids text book and get the theoretical "sweet spot" for the car.

It'll be different for all climates based on air density and stuff like that, but I'll cross that bridge when I get to it.

Just to add my two cents with the new '09 RX-8.

I've got a 2009 AT. I get at worse 15mpg pure city. At best 26 mpg pure highway and currently am running between 20-22 mpg with a mix of both. I have noticed the mpg gradually increasing over time and the car is now approaching 5000 miles.

I'm amazed at some of the mileage you guys are getting. I have a 2007 with 5000k on it and I average about 12-13MPG :uhh:

I drive pretty normal, occasional spirited drive. These are all city miles. My daily commute is only 7 miles each way, could that be the reason my mileage sucks?

Or is there something up here? I didn't expect great mileage, but after reading some of these results it makes me worry something may be amiss.

oh yes.. city mileage will be terrible.

12-13mpg was what I was getting at points driving around Manhattan.

Confirmed my city mileage is 11 to 13mpg in Chicago. The RX is a gas hog in the city.

I have only monitored a couple of tanks so far, just got the car (07 6500km), 14.1mpg on my first tank, and 15.5mpg on my second. The second tank did have premix. Probably 15% highway, 85% city. Driving like I stole the thing 50% of the time.

For only getting approximately 300km a tank, it felt a lot longer than my old car. 01 Grand Am GT. I am attributing this to the fun factor.

I have a 2009 automatic and got 22mpg on the first tank and 21.5 on the second tank with 80% highway and the a/c on.

New 2008 40th Anv. 6 speed, with 1,300 miles. Did a three hour trip at sustained 74-75 mph
through WI I-94. Two people and luggage...total added weight about 350 lbs.
23.3 mpg using 92 octane.
This was way better than expected especially on a new car with such low miles, and running 5W-20 dino oil.
I love this car!!
Kim

after a lot of research, and analysis, i've come to the conclusion of our crappy mpg..

and that is...

our cars are too fun to drive :P

if we had good mpg, then it'd be too good to be true

Hey need help. Without me taking the Rx8 to the dealers, can someone tell me why my Rx8 is consuming a hell of a lot of fuel even when im trying my best not to floor it and stay at the legal speed limit of 30mph (United Kingdom). I have fuelled the car to the max drove it sensibily and it drinks like a horse. Been to a few garages and have been told allsorts. Please help

Hey need help. Without me taking the Rx8 to the dealers, can someone tell me why my Rx8 is consuming a hell of a lot of fuel even when im trying my best not to floor it and stay at the legal speed limit of 30mph (United Kingdom). I have fuelled the car to the max drove it sensibily and it drinks like a horse. Been to a few garages and have been told allsorts. Please help

Please give us the history on your car, year MT/AT,miles etc just anything you can add... The service it's had parts replaced. Give us the numbers on your next fill up or two and well do the math. Most people get 14-16 in city driving.

Please give us the history on your car, year MT/AT,miles etc just anything you can add... The service it's had parts replaced. Give us the numbers on your next fill up or two and well do the math. Most people get 14-16 in city driving.

Registered October 2005, Manual Transmission, 231 bhp,

Serviced by dealers;
26/06/2006
11/05/2007
21/04/2008
28/02/2009
12/02/2010 most recent service (air filter, oil change, spark plug change, oil filter)

2 Weeks ago had the throttle body cleaned, Maf sensor, which got rid of the low idle an shake.

Full Fuel tank filled rite up to the top, gave me 300 miles at 80-85 mph average speed. on the motorway

half a tank gives me 70 miles, was average of 100 miles. so a massive change there differance of 30 miles.

is there any other info you require thanks.

Last three fillups:

1) 47.6731 L @ 1.039 / L - 383.4km ---> 12 L / 100km (19.6 MPG)
2) 48.9240 L @ 1.009 / L - 437.7 km ---> 11.1 L / 100km (21.19 MPG)
3) 46.2020 L @ 1.019 / L - 444.5 km ---> 10.39 L / 100km (22.637 MPG)

Fill #1 was on Co-Op Premium Gas, Fillup 2 and 3 was on Shell V-Power. Mostly highway driving on all 3 and softer driving (less zoom zoom) on #3.

For me, gas vendor (Shell vs Co-Op) seems to be correlated with gas mileage.

James.

I have an 2004 rx8 gt and i get 200-230 to the tank and i have heard turboed cars getting that, my question is what can i do to up that? I've replaced coil spark plugs wires, so what would be left? fuel pump? i have around 62k miles and ive owned it since 29k. Thanks guys

My best mpg pure highway was 20.8. My worst mpg pure city driving was 12.8.

http://www.fuelly.com/driver/silver02tdi/rx8

I usually get about 10mpg driving around town (in winter) but yesterday I picked up a friend from the airport and it did about 26.6 mpg! I was very surprised. this was all highway tho, I was on I-65 doing between 80 and 95 in sixth.

On the 3 fillups we have done on my wife's new 2010 AT, I have averaged 20mpg each time. Premixed. 1100 miles so far. I live on an Army post, so much driving is only 30-40mph, with some trips into town at 65mph or so.

At least one redline trip per drive to keep her happy.

Date Miles Gallons MPG
3.3.2011 130.6 6.837 - 19.1
28.2.2011 108.7 5.812 - 18.7
27.2.2011 124.3 6.604 - 18.8



in reykjavík city iceland

I was getting 200-240miles on a tank when I first bought my 04 6speed. I replaced the plugs and wires within a few days or getting it. It had 28k miles on it at time of purchase. Had the cat replaced under warrenty due to a cat efficeincy code, started getting 240-260miles per tank. Then decided to replace the coils...

First fill-up: 279 miles
Second fill-up: 293 miles
Last fill-up(as of yesterday): 309 miles

The plugs and wires are OEM NGK. The coils are, dare I say it, Duralast! Yes AutoZone coils($24ea.) and I'm getting over 20mpg. Car has 35k miles on it now...Anyone else seeing these kind of numbers???

http://www.fuelly.com/car/mazda/rx-8

270 cars, 1.5 million miles covered so far. Probably the largest set of data available.

Bell curve is centered on 18 mpg. :icon_no2:

I have been getting 16.5 mpg in my 2004 MT at maybe 60/40 highway/city. Last week I pulled the back seat cushion to get at the fuel pump to check the filter sock (just for fun) and found that the plastic outlet fitting was cracked and leaking quite a bit of gas. Yes my car has always had a bit of a gasoline odor at times but I am used to that having owned several Miatas :)

So, I replaced the entire fuel pump assembly last week and it looks like my car is headed for 20+ mpg. The car really runs great and I changed the plugs wires and coils and repaired vacuum leaks when I bought it so it has always bothered me that I could only get 16 mpg. I drive the car hard with lots of high rpm operation just for engine health of course:)

If anyone has the combination of low mpg and some gasoline odor I recommend taking a look at the fuel pump outlet fitting. It's easy to do, just pull up on the front of the driver side back seat bottom to remove it and remove the cover plate (4 screws) and it is right there on top of the gas tank. Be sure to put out whatever you are smoking before doing this!

Cheers!