Hello all.

First let me say... I bought my 8 AFTER discovering about the buyback offer and having read several forums (with many gripes)... this one being the best (board) of course.

Question is... Are estimated MPG ratings as important as the posted HP ratings. I mean, I know the Fuel Efficiency is "estimated" where the rating for HP was marketed at 250 and there's an allowance for +/- 4%. What's the allowable variance in the estimated MPG?

I know I bought a sports car... and I knew it was gonna suck down some fuel... but DANG!!!!

I'm truly hoping it is an ecu issue and will resolve itself after I've gotten a few more miles on it (1268 and going up fast!). Even if the ecu won't change my fuel efficiency after some more time... hopefully an acceptable reprogramming or mod chip will help out.

If the national average of RX-8 owners' fuel efficiency is below Mazda's estimations... will we see another buyback offer?

Anyone know of any incidents where the estimated MPG ratings of a manufacturer was so far off that some action was taken?

Just curious...

Regards,
Wankeler

good question--wish I had the answer

I think the biggest problem is that hp is the same for each car, but gas mileage is different. I suppose if a liittle old lady drove the car the mileage would be better than the way I drive.


I mean a Dyno is a measurement tool for the engine that most people would agree on the results. I don't think the same can be said about MPG. I wish it were better too, but I don't know how you force them to fix a subjective difference. Any Ideas?

Actually, aren't the mileage estimates based on EPA data, from an official EPA course that is run (I'm guessing under EPA's watchful eyes)??

What I find troubling is that the beautiful book that Mazda so kindly sent us states on page 50: Fuel Consumption, U.S. EPA estimate:

High Power Standard Power
City mpg 20.4 20.3
Highway mpg 30.2 31.6
Combined mpg 23.9 24.2

Below this, it shows all the Exhaust Emissions which implies it passed all of them including the so-called tough California Standards.
If it already passed the emissions, then why the drop in horsepower? Frankly I don’t car. A drop in horsepower should provide even better mileage than originally claimed above.

What the Hell has happened to the fuel economy. This is the real issue, not the horsepower. I am a conservative driver and the best I’ve ever gotten on the highway was 19.5 mpg. That’s a 35% drop. I am extremely disappointed with the mileage and I want to know why it is so bad! I am not a happy camper at all.:mad:

I dont own an RX-8, I have (will have) a 350Z but just wanted to chime in and give you RX-8 peeps some of what the Nissan folks have experienced.

I know that a year ago, a lot of people were complaining that the G35S(same engine as 350Z) not getting the EPA City MPG. I check the Nissan forums, and I dont see too many complaints about MPG today. Once in a while, you will get somebody posting about low MPG (usually a person who just bought the car), but then an old-timer will post and tell the newbie that the engine is still breaking in and to give it time.

Could very well be that the Renesis is the same way.

Originally posted by Wankeler
Hello all...

Question is... Are estimated MPG ratings as important as the posted HP ratings. I mean, I know the Fuel Efficiency is "estimated" where the rating for HP was marketed at 250 and there's an allowance for +/- 4%. What's the allowable variance in the estimated MPG?...
...
If the national average of RX-8 owners' fuel efficiency is below Mazda's estimations... will we see another buyback offer?


Regards,
Wankeler

hi Wankeler. the fuel efficiency rating is not mazda's it is the epa's. as for the allowable variance, check the window sicker, if you still have it, below the big bold numbers it show the range. i have my sticker in the car if you don't have yours, i will check it.

and no there wont be a buyback because they are not mazda's numbers

High Power Standard Power
City mpg 20.4 20.3
Highway mpg 30.2 31.6
Combined mpg 23.9 24.2


Man! If I was getting anything close to this I'd be keeping the car. Too bad. It's been fun while it's lasted.

Originally posted by boowana
What I find troubling is that the beautiful book that Mazda so kindly sent us states on page 50: Fuel Consumption, U.S. EPA estimate:

High Power Standard Power
City mpg 20.4 20.3
Highway mpg 30.2 31.6
Combined mpg 23.9 24.2

Below this, it shows all the Exhaust Emissions which implies it passed all of them including the so-called tough California Standards.
If it already passed the emissions, then why the drop in horsepower? Frankly I don’t car. A drop in horsepower should provide even better mileage than originally claimed above.



i too would like to know how those MPG figures printed in the book were derived. the emissions figure there are from mazda's own in house testing not from any governmental testing body. why they would not be closer to the government testing is anyone's gues but i bet there is a shake-up going on in that deptartment with some people losing their jobs. and Brian my real world mpg has gone up about 3 miles per gallon on avg. from 15.7 my first tank to about 18.5 now. also on my hwy trip from portland to monterey i got @22mpg straight highway driving for 10 hours. just letting you know it does get better with more miles on it. 2800+ on mine now

The fuel mileage estimates is done according to a Federal standard. If I remember correctly, for my senior class project we had to use the EPA and Euro mileage cycle to simulate typical loads an engine will experience in use.

All it is is a set of data point which specify time and speed at each corresponding time. Acceleration is calculated by taking the speed divided by delta time.

The city cycle had more stops and more incidence of high acceleration and therefore high engine demand. The highway had a lot less stops and the acceleration is usually gradual so less engine demand. I don't think there is a test standard for sport cars and one for SUVs or one for passenger cars. It's the same cycle across the board.

You can find the cycle at your local engineering library. At least that where we found our data.

That being said, Mazda can easily say that your driving does not reflect the driving conditions simulated by the test standard, therefore the fuel mileage does not match.



Magic8

Originally posted by Tweety-nator
I dont own an RX-8, I have (will have) a 350Z but just wanted to chime in and give you RX-8 peeps some of what the Nissan folks have experienced.

I know that a year ago, a lot of people were complaining that the G35S(same engine as 350Z) not getting the EPA City MPG. I check the Nissan forums, and I dont see too many complaints about MPG today. Once in a while, you will get somebody posting about low MPG (usually a person who just bought the car), but then an old-timer will post and tell the newbie that the engine is still breaking in and to give it time.

Could very well be that the Renesis is the same way.

A friend of mine drives a G35 coupe 6MT....and he cannot get a better average than 18mpg. Least to say he's had his G since before October last year (he flew to a dealer to get his ride.....and got back driving...)

Anyways....
#1 C'mon guys....sports car or sports sedan, or sporty-suicide-doored-gas-muncher: don't expect to be getting 20mpg right off the hat. I used to drive a Rav4 FWD and was getting around 280 miles on a tank with slightly more than 16 gallons...how is that for economy?? Of course its better than the 8 so far...they were consistant 17mpg. :cool:

The best I've got so far: 17.5mpg - my worst: 15.5mpg
The difference?....nothing, similar temp conditions, driving. I am not racing lights, but neither Im driving easy: 1-2-3 go up in revs and then I almost instinctively try to get up to 5th as fast as I can.

Go ahead and look the EPA estimates for a Rav4.....


NOTE: the toyota didn't have anything modified. And the mileage is after a Tune-up and sparkplug change.

Edit: OK, and I almost forgot.....they shouldn't have printed those estimates in the manual or book most of you guys have. However, the sticker EPA #s seem to be within the tolerance of how you drive it: 18-22 (or 24??)

Originally posted by Magic8
The fuel mileage estimates is done according to a Federal standard. If I remember correctly, for my senior class project we had to use the EPA and Euro mileage cycle to simulate typical loads an engine will experience in use.




yes but how did Mazda arrive at the estimates printed in the yamaguchi book, which are so different from the EPA figures that are much lower. hmmm i may have answer my own question. i am going to go look at the window sticker in my glovebox and see why the "high" marks of the range are. i'll be back.


edit: yup the high points from the EPA on the sticker are 21 city and 28 highway, much closer to the figures given in the book. it seems Mazda Marketing had a hand in it again and chose to give the highest rosiest numbers instead of the more reasonable average numbers. that marketing dept needs to pull its collective head out of its collective ass.

I'm going to guess that these motors have not even come close to the mileage point when they are broken in. I know Mazda says 600 miles. My guess is something more like 10-15k miles. I don't own an 8 but if I did the motor wouldn't see more than 3k revs for 1000 miles. Then 4k revs for the next thousand miles and so on up the scale. Yes it would take much longer to break in but that's how I have done the last 6 or so rotaries I've built for myself. ...I think that so much of the bad mileage and some of the HP issues are because the cars just haven't settled into their *groove* yet. I read all the posts where folks have waited 600 miles and spin them up to 8k. Damn.. the motor is starting to break in in the lower rpms and all of a sudden asked to perform in in uncharted territory, break it in gradually, little by little. After you have 10k on it, then spin it up. I would bet that when we see cars with 10-15k on them, a great many of the mileage and some of the HP concerns will be mute. Not to mention the mileage switch. I checked the factory manuals on the 86-91 and the 93-95. That switch happens at 20k. Betting the Renesis is there also. Patience people. Stop and realize the incredible vehicle that you own. This car will only get better with time.... we have not yet seen the total package.

I believe each region (Europe, Japan, USA, etc.) has different cycles. There isn't an international standard, at least nothing I am aware of. So the numbers quoted in the book may be derived from a different cycle.

Again these fuel mileage numbers are just estimates, since they are applicable to all vehicles regardless whether they reflect the real use of a given vehicle, i.e. there isn't a sport car cycle.



Magic8

Originally posted by zoom44
yes but how did Mazda arrive at the estimates printed in the yamaguchi book,

simple....they used an abacus!! :D :D

hahahahahahah abacus....hahahahah:D

Originally posted by RX8-TX


A friend of mine drives a G35 coupe 6MT....and he cannot get a better average than 18mpg. Least to say he's had his G since before October last year (he flew to a dealer to get his ride.....and got back driving...)

Anyways....
#1 C'mon guys....sports car or sports sedan, or sporty-suicide-doored-gas-muncher: don't expect to be getting 20mpg right off the hat. I used to drive a Rav4 FWD and was getting around 280 miles on a tank with slightly more than 16 gallons...how is that for economy?? Of course its better than the 8 so far...they were consistant 17mpg. :cool:

The best I've got so far: 17.5mpg - my worst: 15.5mpg
The difference?....nothing, similar temp conditions, driving. I am not racing lights, but neither Im driving easy: 1-2-3 go up in revs and then I almost instinctively try to get up to 5th as fast as I can.

Go ahead and look the EPA estimates for a Rav4.....


NOTE: the toyota didn't have anything modified. And the mileage is after a Tune-up and sparkplug change.

Edit: OK, and I almost forgot.....they shouldn't have printed those estimates in the manual or book most of you guys have. However, the sticker EPA #s seem to be within the tolerance of how you drive it: 18-22 (or 24??)


Exactly! It takes time for these new-fangled buggers to reach the rated MPG. For some, it may never happen. My current car is a 1999 Subaru Legacy, rated at 22MPG City. I have yet to reach the stated MPG, I only get 20MPG. I would gladly accept a 2MPG penalty at 18MPG to get the kind of "oomph" that only a sports car can provide. :D

Am I like the only person getting decent gas mileage from this car? 18-19 city, 25-26 highway. Yeah, the book was wrong. Books like that are ALWAYS wrong in places. Especially books made for marketing purposes.

I have been getting around 18-19 mpg. I can not complain about
that for rotary. I think that is real good. My 12a rx3sp (2200lbs) would only get 15mgp.

It is a well known fact that rotary engines make little hp/tq for
the gas milage that it gets. On the plus side it is small/compact
low center of gravity, smooth, high reving. Just the thing you want in a sports car.

Fuel economy is based on tests done by the manufacturers on pre-production models. The data is then submitted to the EPA. Verification tests using government standards are then performed on 10% of the autos. All fuel economy results are then lowered by 10% that is the number you see on you new car sticker and in the governemnt fuel economy guide. Please see the following link for more info.

http://www.fueleconomy.gov/

:D

How do you drive it, Elara?

Last week I got 23.1mpg (US gallons) combination suburban and highway, this week suburban only at 21.3mpg. These were tests; smooth acceleration to speed limits (as much as I dampen my enthusiasm to let the car have its head).

If it's pedal to the metal stuff, then you must expect mpg to suffer.

Labrat makes a great point that I think all but closes this issue. Look at how you are driving your car. I drive almost exclusively in the city and on occasion let the car play a little bit. I've been getting just under 18 MPG every tank. You have to expect that when the cars were tested, they were driven under "normal" conditions, not under the conditions that most of us want to drive the 8. That's life. You're going to get lower mileage when you drive the car a little harder, thus a little less efficient.

The difference in driving the car hard or easy goes without saying. I have not ready any posts the dispute that. The matter is not closed when it is obvious that there is way, way, way, way, too much discrepancy between the lowest and highest mpg reported by forum members. BTW if you read the government site i posted you will see that various driving conditions are taken into consideration in testing. Even those estimates are lowered to arrive at the mileage on the sticker. Conclusion: matter not closed something is terribly wrong here, to borrow a line from move.

Originally posted by RX8-TX


A friend of mine drives a G35 coupe 6MT....and he cannot get a better average than 18mpg. Least to say he's had his G since before October last year (he flew to a dealer to get his ride.....and got back driving...)


The worst I have got in my G35C is something like 14mpg.... this is from driving hours after hours in only the first 2 gears in city traffic. The best I have gotten is on a long highway trip that gave me around 28mpg. (cruise control at 70mph up+down hills for hours) Those dreaded city travel averaging under 10mph is really killing me.

Originally posted by Skyline Maniac


The worst I have got in my G35C is something like 14mpg.... this is from driving hours after hours in only the first 2 gears in city traffic. The best I have gotten is on a long highway trip that gave me around 28mpg. (cruise control at 70mph up+down hills for hours) Those dreaded city travel averaging under 10mph is really killing me.

Kindda know what you mean. But this guys doesn't complaint....he bought his G knowing he was getting a 350Z in disguise (...possitive comment, alright??..Im not bashing anything)

And he's dealing with it. IN fact, he's been happy with the car so far...except for a few glitches that took him back to the dealer for a day or so (passenger power seat was somehow stuck, nothing major..)

Originally posted by RX8-TX


Kindda know what you mean. But this guys doesn't complaint....he bought his G knowing he was getting a 350Z in disguise (...possitive comment, alright??..Im not bashing anything)

And he's dealing with it. IN fact, he's been happy with the car so far...except for a few glitches that took him back to the dealer for a day or so (passenger power seat was somehow stuck, nothing major..)

Hey, nothing wrong in saying that the G is a 350z in disguise... in my opinion thats a compliment. :D

Originally posted by zoom44


hi Wankeler. the fuel efficiency rating is not mazda's it is the epa's. as for the allowable variance, check the window sicker, if you still have it, below the big bold numbers it show the range. i have my sticker in the car if you don't have yours, i will check it.

and no there wont be a buyback because they are not mazda's numbers

Just thought I'd chuck in my $.02 as my first post. The sticker says the range for city is 15-21 mpg and 20-28 for highway. That sounds consistent with what most people are getting, though granted we all fall on the bottom side of that range. I don't think there's been any misrepresentation about the economy. My '98 stratus claims it gets 28 mpg and even on a 2000 mile cross-country trip I never broke over 25. I think you'd have to really nurse any car to get the numbers they put on the sticker, but I'd like to hear if that's been everyone's experience with other vehicles.

And for the record my car (VIN 02196) has been getting a consistent 19mpg in mixed highway/city. My worst is 15 (pure city) and best was 23 (pure highway).

Originally posted by Elara
Am I like the only person getting decent gas mileage from this car? 18-19 city, 25-26 highway. Yeah, the book was wrong. Books like that are ALWAYS wrong in places. Especially books made for marketing purposes.

Man, if I were guaranteed to get those mileage numbers, I would easily have bought an RX-8 already! I was just about to get one when I read about the widespread mpg problem, and it really made me hesitate.

By the way, Elara, is your RX-8 one of the first ones that were held up at port?

It doesn't sound like most of you guys ever owned a naturally aspirated (or even turbo) rotary before but I know some have. My 1st and 2nd gen RX-7s only got about 18mpg when I was good to them and that was with around 100 LESS horsepower than the Renesis! The turbo II averages even less. The 2nd gens were rated at around 18/24mpg. The 18 was only attainable if I drove it like grandma. It is very noticable to gas mileage if I had done even a little spirited driving on a tank or if I hadn't. I only got the 24 mpg number a couple of times and that was on the freeway after I had done alot to the car and leaned it way way out. Look at the people on here who have more miles on their cars. They make more power and get better mileage than they did when they were purchased. Since the car is drive (throttle) by wire and very computer controlled it is feasible to think that it is in fact programmed with a break in type of period in mind. Mazda knows that many people are not going to break in their engines. A fantastic example of this is anyone who dynoed their cars before they had a couple thousand miles on them. You can't tell me that everyone waited until after 500 miles to rev the engine above 5000 rpm and until after 1000 miles to even approach redline for the first time. Anyone get the oil changed at 500 miles and then again at 1000? No one should have floored it for the first time until after 1500+ miles. No one does this and that is the recommended breaki n for all previous rotaries when an engine dyno isn't available. As an engineer with the available technology I would have definitely programmed in a break in period since most people don't know how to be patient. Pick almost any thread on here for proof. Running it rich and holding back some high rpm power for a while are great ways to do it. Everyone wants it in writing that the ecu does this but the evidence seems to point at this from other peoples results. Mazda spent tons of time and money on the 3rd gen engines by breaking them in at the factory on engine dynos. There are some neat pictures of these huge rooms of engines all running. Too bad they took shortcuts on other aspects of that car. All of the rotaries are still hand built and it takes tons of time to load them all onto engine stands for break in. I'd just put them in the cars and have a steadily reprogramming ecu. It all makes sense to me. Here's a great idea. Go to sevenstock 6 in 2 weeks and ask the main Mazda guys there whats going on. They'll be there, even the RX-8 program manager as well as one of the developers of Mazda's rotary engine. I still think there will be no problems with the ratings on the sticker once the mileage gets to a certain point. I still remember back in February when people said I was dumb (OK maybe I am!) for thinking that there was also a 4 port Renesis on the way in the auto and we do have it. Time will tell this one as well. The book was preliminary info. I love the car never the less and couldn't really care less either way. The rotary is back and with a little more time we'll be able to reprogram the ecu for better power and fuel economy.

Originally posted by commentator
The difference in driving the car hard or easy goes without saying. I have not ready any posts the dispute that. The matter is not closed when it is obvious that there is way, way, way, way, too much discrepancy between the lowest and highest mpg reported by forum members. BTW if you read the government site i posted you will see that various driving conditions are taken into consideration in testing. Even those estimates are lowered to arrive at the mileage on the sticker. Conclusion: matter not closed something is terribly wrong here, to borrow a line from move.

Here, here. I have been getting 13mpg all the way to the 1500 mi mark I am currently on. This last tank I went with 89 octane and turning DSC/TSC off. I can already see the mpg will improve by about 2-3mpg. interesting, indeed - but not too surprising.

I have a theory about the wild mpg discrepancies. And, I know a way we can verify this theory. The theory is based on an analogous situation I face at work. I work in the cell phone industry as an engineer. When a phone is flashed (programmed), you typically have to replace the phones "tuning parameters". Every phone is different due to variances in the individual parts (chips & components) & the tuning parameters compensate for these variances. I thoerize that the car's motor & ECU system is similar w/ similar tuning parameters. When they were reflashing the ECUs at the ports, they may have botched up the tuning parameters for some 8s.

The way to validate this is based on a simple premiss: whatever is coming out of the factory now is getting the proper tuning parameters. If that is true, then the cars coming out of the factory after the port campaign should be getting better mpg.

Maybe we need a new poll?

I just checked yesterday morning and calculated 20 mpg. Well technically it was 19.9 but I'm being optimistic. :) That's with DSC still ON and mixed city/highway commuting. What I can figure is that I'm not sitting at lights as often as some folks so I don't idle as much. Dunno, I know it could always be better but so far I'm ok with the mpg I'm getting. It certainly has improved as the car gains more miles.

Originally posted by Superbone
How do you drive it, Elara?

If I'm cruising for any length of time over 30, it's in 5th. Over 40, it's in 6th. On the highway, I usually skip 5th, and sometimes 4th and go right from 3rd into 6th. But most of my driving is stop and go in the city, and I'm not babying it- redlining at least twice a week. Maybe I'm driving like the proverbial grandma. But I'm not doing it on purpose.

On the tank I'm on right now, I've got 230 miles and just over a quarter of a tank left to go. This is half city half highway.

Gs are getting anything between 14 - 24 mpg (depending on transmission and driving habits)...if anyone would like the source, PM me....I won't post any address just in case we have pyromaniacs roaming around...

When I had my WRX, I would get consistently 19-20mpg. I noticed that when I was out of town and my girlfriend drove the car, she got way better mileage than I did (like 25 mpg). I thought I was being conservative enough with my driving, but obviously not enough. I then tried being very, very conservative. Shifting around 3-4k, staying off boost most of the time and most important, being light on the gas pedal to stay on the range of the ECU where it is using the 02 sensors adn not just the fuel maps. Well, immediately my mileage jumped to 23-24 mpg. Very significant difference!

It also proved to me that I could either have fun with the car or have good mileage.

At least with the RX-8 you can run low octane!

Originally posted by Elara




On the tank I'm on right now, I've got 230 miles and just over a quarter of a tank left to go. This is half city half highway.

hey me too, well actually like 228 at a quarter. when i first got the car the light was coming on by 210 and was on the E by 220 in mixed driving.

Originally posted by Monster8


The sticker says the range for city is 15-21 mpg and 20-28 for highway. That sounds consistent with what most people are getting, though granted we all fall on the bottom side of that range. I don't think there's been any misrepresentation about the economy.


I have to respectfully disagree with that assessment. If the sticker says city driving will get you 18mpg with a range of 15-21 mpg, then I would expect the mean, mode and median mpg from city driving to be 18, and 15 and 21 to be at least one standard deviation to either side of 18. Falling within the range doesn't cut it. If they say 18 with a range of 15-21 and everybody gets 15, they've essentially mispresented themselves, statistically and otherwise. (I'm not saying they've necessarily done that intentionally, although I'll leave that open to the conspiracy theorists to debate.)

Of course, the posters to this forum are self-selective and probably not a normal sample (the ones who get below 18 come here to complain while the ones who get over 18 never bother to post anything), but still... show me the person who got 28mpg doing highway driving!

From the numerous posts I've read on the fuel economy issue, it sounds like the sticker should say city driving will get you 15.5mpg, with a range of 13-18mpg.

just to chime in...

The EPA numbers have been right on, or slightly low, for every car I've owned...

My 1990 Bonneville, the numbers were pretty even, until some fuel sensor broke
My 2001 Neon, I actually got slightly higher highway mileage than the EPA said I would
My 2003 WRX, the EPA says 20/27 city/highway, and with about 60/40 highway/city I get about 24 mpg... and I drive the car pretty hard (spend a healthy amount of time above 5000 rpm)...

That's very interesting that the EPA does their testing on preproduction cars however... might explain a lot...

-bd

Originally posted by newport8


I have to respectfully disagree with that assessment. If the sticker says city driving will get you 18mpg with a range of 15-21 mpg, then I would expect the mean, mode and median mpg from city driving to be 18, and 15 and 21 to be at least one standard deviation to either side of 18. Falling within the range doesn't cut it. If they say 18 with a range of 15-21 and everybody gets 15, they've essentially mispresented themselves, statistically and otherwise.....
From the numerous posts I've read on the fuel economy issue, it sounds like the sticker should say city driving will get you 15.5mpg, with a range of 13-18mpg.

if by "they" you mean Mazda then no they haven't. it is not up to them what numbers or range of numbers are on the sticker as the mpg rating. that is entirely up to the EPA and the numbers the calculate during testing of the vehicles. also as one of the many people who have mentioned it , the cars are getting better mileage the more miles they have on them. most off the people who have 3k+ miles on their cars are getting 18+ in city driving now- my tank i finished last night was 18.4 mpg. my last highway tank was 23+.

I can live with 18mpg it was the 13mpg I got for the first 2k miles that was tough. It seems once I hit around 2k mpg has risen up to 18