BillK

Seriously - most of it is driving style; perhaps Mazda should have enabled an upshift light.

Simply put, if you shift at 6000 RPM you're going to get worse mileage than if you shift at 3000, and the name of the game in mileage is to get to sixth gear as fast as possible.

Try this city folks - shift 1->3->6, shifting at around 3000 RPM from 1->3 and into 6th as soon as you get to speed. Odds are the engine will be turning at around 1000 RPM and 40 MPH or so. Do this for a week and see what your mileage is.

Also, be sure you never idle longer than one traffic light; being stuck in traffic sucks gas like there's no tomorrow.

As far as highway MPG is concerned, what speed are you going? I assume you are driving in sixth, but most cars suffer a drop in MPG at speeds of 70 MPH and above due to increased drag. Set the cruise at 60 MPH and see what kind of mileage you get; it will be higher than what you get at 75. Don't forget to hack off 1-2 MPG if you have the rear spoiler.

There are those who will cry "3000 RPM? Why did you buy a car like this?" Hey, feel free to rev it high, but remember doing so comes with mileage consequences.

RX-8 Zoomster

Good post BillK! Ditto on every point.

MVCalypso

OK, after several tanks of terrible mileage, I just decided to ignore it and drive the car. I expected the mileage to drop when I went back to running the air conditioner and shifting above 3k - much to my suprise the mileage has increased significantly for the last tank. Weird.

Here are the things that changed: 1) the total OD for the last tank was between 750-950 ( change in ECU mapping?); 2) I happened to change gas brands (from Chevron to 76). 3) Same combo re city/freeway driving - no sig change in pattern.

On the immediately prior tank I got 13.63 MPG; on this tank I got 15.62... that's a 24% difference. The best I had been able to do before was 15 wtih all granny driving and no air.

Wish I knew whether to attribute this to the gas brand or the total mileage. Guess I won't really know until I track things for a few more tanks. I'll be sticking with 76 for while to eliminate that variable.

Of course I'm still a long way from even the EPA city estimate. Perhaps if I keep the fingers crossed and continue sacrifcing virgins to the MPG gods... Or I suppose I can decide to have terrible angst over the horse power issue and let Mazda have the car back.

Dave

Doug DeBug

Took a quick trip from Dallas to Austin last Thursday and paid close attention to my MPG. This was about 98% highway due to the fact that I live just blocks from the highway and my destination was a mere 6 blocks from the freeway exit. I had the air on and took it easy on my speed keeping it under 70 most of the way. I took advantage of cruise control when I could and didn't do any aggressive driving. Anyway...I only got 21.3 MPG but expected more for driving like grandma. My city driving is aggressive and I feel lucky to get the trip meter over 200 before the low fuel light comes on. My 4000 pound Pickup truck with it's 5.7 V8 gets slightly better mileage than my 8 but isn't doesn't quite have the same driving experience

DeBug

BRealistic

From http://www.fueleconomy.gov/feg/driveHabits.shtml


Drive Sensibly

Aggressive driving (speeding, rapid acceleration and braking) wastes gas. It can lower your gas mileage by 33 percent at highway speeds and by 5 percent around town. Sensible driving is also safer for you and others, so you may save more than gas money

Fuel Economy Benefit:
5-33%

Equivalent Gasoline Savings:
$0.07-$0.49/gallon

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Observe the Speed Limit

Gas mileage decreases rapidly at speeds above 60 mph. Each 5 mph you drive over 60 mph is like paying an additional $0.10 per gallon for gas. Observing the speed limit is also safer.

Fuel Economy Benefit:
7-23%

Equivalent Gasoline Savings:
$0.10-$0.34/gallon

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Avoid Excessive Idling

Idling gets 0 miles per gallon. Cars with larger engines typically waste more gas at idle than do cars with smaller engines

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Use Cruise Control

Using cruise control on the highway helps you maintain a constant speed and, in most cases, will save gas.

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Use Overdrive Gears

When you use overdrive gearing, your car's engine speed goes down. This saves gas and reduces engine wear.
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//////////////////////////


For the record, I have a big problem with the way the EPA figures the MPG ratings for vehicles.

from http://www.fueleconomy.gov/feg/info.shtml#estimates:

---------------------------------------------------------------------------------


How are fuel economy estimates obtained?

The fuel economy estimates are based on results of tests required by the U.S. Environmental Protection Agency (EPA). These tests are used to certify that vehicles meet the Federal emissions and fuel economy standards. Manufacturers test pre-production prototypes of the new vehicle models and submit the test results to EPA. . EPA re-tests about 10% of the tested vehicles to confirm manufacturer's results in EPA's lab. 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.

There are two different fuel economy estimates for each vehicle in the Fuel Economy Guide, one for city driving and one for highway driving. To generate these two estimates, separate tests are used to represent typical everyday driving in a city and in a rural setting. Two kinds of engine starts are used: the cold start, which is similar to starting a car in the morning after it has been parked all night; and the hot start, similar to restarting a vehicle after it has been warmed up, driven, and stopped for a short time.

The test used to determine the city fuel economy estimate simulates an 11-mile, stop-and-go trip with an average speed of 20 miles per hour (mph). The trip takes 31 minutes and has 23 stops. About 18 percent of the time is spent idling, as in waiting at traffic lights or in rush hour traffic. The maximum speed is 56 mph. The engine is initially started after being parked overnight. Vehicles are tested at 68 F to 86 F ambient temperature.

The test to determine the highway fuel economy estimate represents a mixture of "non-city" driving. Segments corresponding to different kinds of rural roads and interstate highways are included. The test simulates a 10-mile trip and averages 48 mph. The maximum speed is 60 mph. The test is run with the engine warmed up and has little idling time and no stops (except at the end of the test).

NOTE: To make the numbers in the Fuel Economy Guide more useful for consumers, EPA adjusts these laboratory test results to account for the difference between controlled laboratory conditions and actual driving on the road. The laboratory fuel economy results are adjusted downward to arrive at the estimates in the Fuel Economy Guide and on the labels seen on new cars, light trucks, and vans. The city estimate is lowered by 10% and the highway estimate by 22% from the laboratory test results. Experience has proven that these adjustments make the mileage estimates in the Fuel Economy Guide correspond more closely to the actual fuel economy realized by the average driver.
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I don't see this 'test' preceedure changing- based on the sales of trucks and SUVs. This is done on a treadmill??? So the aerodynamics of the vehicle have NO effect on the EPA's numbers, and even then they DON'T even go faster than 60mph? What a bunch of BS. No wonder vehicles can really suck the gas on the interstare when going 80mph when compared to the EPA 'rating'. And they never give the vehicle more fuel than what is needed, and no hills. (no full throttle )
Anywho, keep in mind that they don't test with the a/c on, and have wide sticky tires really has a less effect on a treadmill only running the drive tires than on the hot pavement with all four running.
You guys not getting very good fuel economy numbers with your RX-8s, try running the tires at closer to maximum pressure and keeping the car in the highest gear possible until you absolutely must have the extra power. My bro bitches about the fuel economy of his Miata, but he 'cruises' around in third gear all the time, even when going a steady 60mph. We have had arguements about this when I am forced to ride with him.
Also, try running incognito on the highway. When I drive on the interstate or any four lane, I always stay as far right as possible. That way when and if you are speeding, you will attract much less attention from the police. But it also lets you get some draft off of other cars/trucks on the highway. Better fuel economy and less speeding tickets.:p

TJRX8

Just finished another tank of 93 Octane and got a whopping 16!!! mpg. Combined but mostly Highway speeds and very little horsing around.

Mitch Strickler

To BRealistic. Thanks for lots of info, and I agree with most of what you say, but there is one statement that makes me wonder. You say there are no hills (simulated, of course, on the treadmill) in the EPA test. I looked at what seemed to be the same EPA page you printed, and didn't see anything to back that up. They talked about the course including typical rural and highway roads. I would bet even money they dial in the gentle grades of interstates and occasional steeper ones to imitate typical rural roads. But I'm just guessing. If anyone knows, speak up.

Mitch Strickler

To BRealistic. Thanks for lots of info, and I agree with most of what you say, but there is one statement that makes me wonder. You say there are no hills (simulated, of course, on the treadmill) in the EPA test. I looked at what seemed to be the same EPA page you printed, and didn't see anything to back that up. They talked about the course including typical rural and highway roads. I would bet even money they dial in the gentle grades of interstates and occasional steeper ones to imitate typical rural roads. But I'm just guessing. If anyone knows, speak up.

Mitch Strickler

RX-8, I don't appreciate your condescending attitude. You tell us that your wife has achieved good mileage with careful driving. And you at least strongly imply that the rest of us either don't know how to drive for economy, or are whiners.
I see. You know how I drove my car when I got terrible mileage. You have taken apart my RENESIS, and know that it is capable of giving good mileage. You're a remarkable fellow.
I am more patient than some of you young folks (I'm 71), so I have continued to do granny driving through a 1,000 mile breakin period with my auto. That means very rarely hitting even 5,000, and spending almost all the time between 1,500 and 3,000. With much more vigorous post-breakin driving, I have attained EPA highway mileage in many other cars.
My car, ordered the day after they started taking orders, was an early build. The evidence seems to show that it is not performing up to par. With all due respect, I will trust my reasoning power over your comments.
Mitch

TJRX8

Yeah. What he said!

RX-8 Zoomster

Mitch,

I assume you are talking to me. If so..... I don't appreciate your condescending accusations. And my aren't we the sensitive fellow.

I was just making a point that there are many factors involved in how one gets results in their MPG's. Driving techniques, driving conditions, driving enviroment, and the vehicle you drive. Only you can determine what is factoring in if you have lower gas mileage. If you don't think your problem is not any of the first three, then obviously you think it's your car. My car seems to be getting as advertised. And quite a few here got close to EPA results in less than desirable driving conditions also. That not to say you're car is not the culprit.. But I feel it is not a widespread problem common to every car. But that's MY opinion. And you don't have to be a smartass to suggest that I think the engine is not responsible in some cases.

In all due respect, I also trust my reasoning power from the results I am getting. If you don't like mine or anyone's elses advise, suggestions, or experiences, and wanting to share that, then you are more than welcome to ignore them. And if you misintrepet my comments as me having a condescending attitude - I say to you - so what?

Mitch, I'm sorry that the RX-8, to you, does not meet all your expectations. If you are really unhappy or disappointed in the vehicle because of the gas mileage, you now have a "free" option to opt out with Mazda's buyback. Then, you'll have the opportunity to purchase a vehicle that may be more energy conscious for you.

Or if you feel that the RX-8 is the right car for you, I hope your mileage will improve through time or via a "fix" if it turns out to be a problem with your engine.

P.S.
Let me add that I am not insensitive to those that feel the car is performing submar in the area of MPG's. If it turns out to be a widespread problem, then I do sincerely hope that Mazda can "fix" whatever might be wrong, and everybody will be happier.

RX-8 Zoomster

HEY!

pelucidor

Just finished my 4th tank and got slightly over 18mpg. Car has a total of 907 miles now, mostly Houston (i.e. city) driving and always with aircon on and windows closed. I tend to go up to 6000rpm in 1st gear and sometimes goto 9000rpm in 1st and 2nd (hear the chime regularly). I would say I redline about 10+times a day. However I also tend to use 5th and 6th a lot when there is no scope for spirited driving (e.g. dawdling in traffic at 30-40mph), or during steady 85mph highway speeds.

I am slightly disappointed in the fuel economy, but it is improving by leaps and bounds as the engine breaks in - my first tankful averaged 15.5mpg and I never exceeded 6000rpm (mostly stayed at 3000rpm). My average over 900 miles is 17mpg and rising. Lots of soot on the tailpipes every day too, and no oil needed so far.

8_wannabe

These comments are not directed at anyone in particular; it's more of an observation I've had in this RX-8 forum and is a generalization of what Mitch said. Some of us have observed "anomolies" in our cars (low mpg and cycling a/c come to mind.) Others don't observe those problems. Those that don't typically make some constructive comments (is a/c set to recirc or what RPM do you shift at, etc.) However, once that has been established they tend to not believe those of us reporting the problem. Like, "Are you sure you're not redlining?" or "Are you sure you've set your a/c temp to low?" This starts to get annoying to the point of condescending. Yes, we know how to operate a/c. Yes, I know how to drive like granny. And yes, my a/c still cycles and I get 17 mpg under the very best of circumstances (15.5 is more typical.) You'd think I'm reporting that I'd seen Sasquatch and the unbelievers out there are calling my bluff. While we do express many different opinions in this forum, when we objectively state observations (as opposed to expressing opinions) please believe that other members know what they're talking about. I think this is what Mitch was reacting to, and I have to admit it does get annoying at times. Some of us, despite our best efforts, are getting ****-poor mileage. Now, let's get down to work and see if we can figure this out so we can hold Mazda accountable. After all, isn't sharing our knowledge to optimize our RX-8 experience what this forum is all about?

astrlsrfr

I agree with Mitch and 8_wannabe. Thanks for the constructive comments. To me, I think some people think we are bashing the RX-8, and are trying to defend it vohemently. This is simply not the case. We just want to know why our cars are missing their stated mileage claims by so much, and so consistently.

I for one, will be speaking to my dealer this week about the buyback option. My plan is to buy a new RX-8 w/ the NAV option. I originally wanted to get this - but was unwilling to wait for it in a later allotment. So now I get a second chance

I will explain to my dealer about the poor gas mileage situtation w/ my current 8 , and that I expect it to be resolved, should I repurchase another one. I figure its prolly just a tuning issue with certain early 8s, and its been quietly resolved. Hopefully, at the very least, they will have a fix for this and a TSB will be made available.

8_wannabe

Hey astrlsrfr, welcome to the forum and to the family of San Diego owners. We had a rally last month and planning another sometime soon; check for thread in the western region area. and thanks for weighing in on this issue.

BRealistic

double post! :p

Yeah, you may have a point. I looked at all this EPA stuff a year ago, when my truck wasn't even close the EPA highway number even when driven like a granny. But recently I got a tank over the EPA hwy number, and it was mixed hwy and city- so who really knows how the get the best fuel economy. It really shocked and pissed me off when I saw the 'scientific lab testing' done. WTF. Never going OVER 60mph? Because of the strict CAFE regulations and steep fines, it is only logical than the auto manufacturers would be designing their vehicles engine mapping and trans gearing for the best EPA results without regard for real world conditions.

One thing to remember, the rotary engine has different metals sandwiched together. When they are cold and the different metal parts havn't fully expanded, they are very inefficient.
Also, any new vehicle owner can demand the dealer do a fuel consumption test, to verify that the car is running properly and using fuel at an acceptable rate. If they refuse, then use the 'buy-back' card to sway their opinion. Of course, they may want a used like new low miles RX-8 to resell, so who knows.
On the buy-back thing: What happens if you traded in a vehicle on your RX-8?

BillK

You get your money back for the RX-8.

Obviously you sold your trade-in to the dealer and were paid an amount for it in credit against the RX-8. That's exactly what you'll get back.

BillK

If you really want to try and get the MPG on the sticker, you probably know you can't keep going to 6K and sometimes 9K in 1st and 2nd. Likewise, you can't go down the highway at 85MPH. Of course I'm sure the state patrol could help you with that one. :D

Seriously, to improve your mileage, try just driving the speed limit; remember as you go much faster than 60 MPH wind drag will start bringing down your MPG precipitously...

eccles

Filled mine up again last night. This time it was a combination of city driving, a 200-mile country trip including considerable time spent at or near triple digits, and about 40 autocross runs. 14.71mpg. I was expecting much worse.

tpryor

WOW! What about tire wear?

Mitch Strickler

Thanks, 8_wannabe and astrlsrfr. You understood exactly what I was saying, and said it better.
The idea of using the buyback and then getting a new car sounds promising, especially if you have one of the cars that was built early -- I was told April 19 -- and then took a suspiciously long time to deliver (tinkering with subpar engine?).
It's not for me, though. In a perfect confirmation of the saying that no good deed goes unpunished, I was within a few hundred yards of the place where I volunteer to read for the blind when an 80 year old woman, upset because she had lost her way going to the hospital, decided to go from the middle lane (of 3) to a right-hand turnoff. She hit four out the five panels on the left side of my car.
The guys at my dealer's body shop thought it might be months before they get the parts for the repair. The car runs fine, but I am worried what will happen when they repair the outer part of the four-welded-panels "ring" that is a key structural part.
Mitch

8_wannabe

Maybe she was one of the ladies you were supposed to read to. LOL. Anyway, bummer about the car. If you can get pix, start another thread and post 'em. You must have a 14-yr-old grandkid who can do digital photos for you.

crazydrifter

okay i dont want to be rude to anyone of you cause heck i dont know you well enought to B**ch slap you but you really are going to listen to the EPA when they dont test rotary motors? hears the deal with your RX8...first off you get lower gas mileage on any car when you have the A/C and with the more electronics you have on when driving the car..with that said if you read about your RX8 the 18 mpg in the city is a average the epa got...that means you should get between 15-21 mpg...well no one here so far has gotten to 18 but here is why...first off granny driving makes the rotary motor burn more gas...instead of shifting at 3000rpm shift at 7000 but dont floor it to 7000....agressive driving is when you floor your car.... i will tell you guys how in my opinion a rotary motor works when it comes to gas...you could say its like a bike...for example lets say you have a 21 speed bike and its in 12th gear...if you start from a stand still it takes more leg power to get the wheels to start to spin but once you get them spinning it gets much easier and you dont have to put in as much leg power...just like a rotary...when you rotary motor is at 3000rpm its like being in the 12th gear and going slow...and when you get the car above 5000 its like being in 12th gear and going relatively faster so the motor doesnt need harder combustion to get the rotar to spin fast like the motor did when going from 1000rpms to 3000rpms....if you dont under stand this just pm me....i found this to be true cause when i went to the dealer to ask about mpg they told me that you get better gas milage the longer you stay in gears...and if you read the post most people getting good mpg are driving the car not granny driving...

8_wannabe

Thanks for the suggestion: I also called Mazda customer service and they referred me to the "fuel consumption test." Spoke next with the service tech at the local dealer and guess what... the test is exactly what you jokingly said. They keep the car for a week, drive it around, take it home at night to validate the claim of low mileage. I seriously thought he was joking, but he wasn't. So I asked, let's say you validate my claim of low mileage, how does driving it around help diagnose the problem? The answer to that is, as they drive it's hooked up to a computer that takes some kinda readings to verify settings and metrics.

I dunno... the whole thing sounds kinda screwy to me. But since I'll be out of the country all next week and when I get back I need to decide whether or not to return the car, what the heck... drive away! I'll have them do this test and I'll post the results sometime after Sept 9th after I get the car back. If they find a way to get me 20 mpg (vice the ~16 I've been getting) it'll be worth it to me. If not, I give back the car. It's a no-lose proposition but they'd better not put 800 miles on this car while I'm gone.