Wankeler

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

mikeb

good question--wish I had the answer

mmjames

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?

KyngNothing

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)??

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.

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.

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.

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

Superbone

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.

zoom44

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

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.

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

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.

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??)

zoom44

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 ***.

Habeeb

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.

Magic8

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

RX8-TX

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

zoom44

hahahahahahah abacus....hahahahah:D

Tweety-nator

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

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.

racerx7

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.

commentator

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

Superbone

How do you drive it, Elara?

labrat

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.

mamccubbin

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.

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.

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.