This fuel economy thing is an important issue, or so it seems from this website, that Mazda needs to address. If this happens at all (and is not driver or conditions related) on any RX8 Mazda really needs to pay attention.

This is not the first, nor the last post about this issue. Anyone getting 13-10 mpg needs to scream and complain until something is done. Like I've told Howard, document your problem with pictures, recepits, video, and other drivers driving your car or else they are just going to make excuses for the problem.

Good luck, I hope the day I get a RX8 I can get at least 17/23 because 13/18 SUCKS!!!!!

 

warm your cars up people makes a humongous difference, and warming up isnt the revs getting back down to normal idle, wait till that temp guage makes it way to normal operating temperature.

 

Im getting 11.8 +/- since i got the car. I only have 2.5k miles on it, but I dont think having to warm a car up FULLY before drive acceptable, I dont have time for that. I let it get the oil circulating for 30 sec. and I go.

I wish they would figure this out. Im only getting 150 miles to the tank !!

 

You are suggesting letting the car sit, running for 10-15 minutes in one's driveway before driving off as a way to conserve fuel? First time I've heard that; do you have any data to show?

 

5 minutes is usually plenty to get it into the beginning of the normal range, you'd be surprised. i ran basically cold when the weathe got cold and got 145 miles out of the tank (10.7mpg blech), but then i decided to be patient with the car and let it warm up on these cold days and got 225 miles (16.6mpg) from the same mix of 95% city driving...plus the real bonus, not having to sit shivering in a car while the heater warms up. so it isnt quite 18 mpg but its still a lot better than the 10.7 i was getting before.

 

I'll give it a shot on my next tank thanks!


btw, I'm wondering if some of the fuel issues are the result of the throttle-by-wire system...seems plausible the computer could be messing up the amounts of gas injected relative to the position of the pedal. Could explain the drastic differences between cars. Seems easier to believe than actual differences in the motor between cars, no?

 

I've seen the opposite effect -- especially when temps are down low like this morning. Letting it idle at 10F for 15 minutes won't bring it up to operating temp, and is just wasting fuel... and the renesis seems to run very rich at during warm up at idle. The worst mileage I had was last February, trying to let the car warm up to take my daughter to school when it was way below zero (~-15F) out every morning for a week straight, which netted me about 13mpg. The temp needle never budged just sitting there idling at those temps.

My advice is to let it idle for a minute or less, then drive it mildly for 5-10 minutes to bring it up to temp faster and the rotary into it's 'happy zone'.

 

i think it has a lot to do with two things...the ECU learning process and the wiring in the MAF sensor.

 

I think you're on the right track, but instead I think differences in the MAF sensor might be to blame (CanZoomer has noted that there are big differences between cars that have installed his CZ piggyback). I think some of the MAF's might be sending falsely high AF readings, making the ECU dump more fuel in than needed. It would be an interesting experiment to swap MAS units between cars with crappy mileage and normal mileage to see if that makes a difference.

 

yeah brought the car in today, last week on the phone they said it was due to the car not having over 1000 miles on it yet. Then i told them well the car has 1800 miles on it and they said nothing. Today they said it was cause the car had below 3000 miles and had not had its first oil change. What it gods name does the oil change have to do with my gas milage? for one i have been adding oil to it so it isnt like the oil has not even been touched. and second it has nothing to do with that ****. Then he asked how i drive, i told him it didnt matter if it was 8grand or 4 grand when shifting, i was getting the same MPG. Then he had the audacity to ask me did i buy the car for good gas milage...haha i laughed and said no, and said to him but when a car is getting 8 miles less to the gallon something is wrong. he said it was cause off the gas and it being winter. I tell him i put in vpower, well most car get bad milage in the winter, and i ask again 7 miles less to the gallon then normal?? and has no response. I feel i am going to be writing a letter of some sort to mazda. If the service manager is goign to keep trying to blow smoke up my *** then im going to, before that though im going to the owner of the dealership because he is a family friend. And if he cant get it done then i will keep goign higher up the ranks. I mean if i was getting like 16 miles to the gallon that could show that i drive hard once in a while, but 10.8??i should be getting almost 80-100 more miles with the amount of gas the car is using.
Thanks guys i just had to vent about this.
Robert
P.S. i notice if i sit in the driveway when the car is cold in the morning and let it sit for a while running it eats a **** load of gas. So nothing is really working for me.

 

You should look for another dealer... I don't know what can be done, but their apathy is a dead-end. If you could talk a dealer into letting you try a new MAF out for a tank I'd be very curious of the result. We're in the same area (same weather/temp), using the same blends and brand of gas, and I'm gettin ~16mpg in all city, fairly agressive driving so far this winter... that's a pretty big delta between our results. I also have a 60lb speakerbox in my trunk, and I'm not exactly skinny .

What is your approx Vin#, if you don't mind sharing?

 

I don't think the vin numbers and date built are necessarily the issue. My car was built in 9/03 and I have not experienced the flooding issues or ridculously low gas mileage. (Avg 19) My 8 has all the recent updates and so far/so good. I beleive there is something going on with some cars (possible defect in something) that is causing people to get 10-13 MPG. I have a question for people with bad gas mileage, is there a great deal more smoot on your tailpipes than should be expected? If so, IMO the car is pumping more gas into the engine than it is actually burning effeiciently. I'm not a mechanic, but just my thoughts.

 

I have black on the tailpipes, but i thought that people on here were saying that this was normal for the 8's. I just want the car to get fixed, i mean this is bad, and i dont even have anything in the trunk. it is just be driving around!
Robert

 

my car has black icky smoot on the pipes too - I got 17.8 w/ my first tank, 15.8 on my second. So far my third seems to be closer inline with my 1st, after 3/8 tank.

 

I mentioned this on another thread, but hadn't heard anything - so: I seem to recall that replacing the thermostat on the RX-7 (from 170 to 190) would increase the mileage (w/ a slight performance hit). Just curious as the whether some type of modification on the 8 might have similar consequences (at least in cold weather letting the engine warm up quicker).

Just a thought...

 

Same here with the 9/03 build. I usually get about 17 mpg with suburb driving(I don't know if that's what they mean by city driving, but when I think of city i picture driving around in traffic stopping every 30 seconds) Also, I always rev it before I shut it off and have never had a flooding problem

 

That's normal for every car

(sorry I don't know how to quote two different posts in one)

 

how do you know that your car was never flooded before you owned it?

brilliantblack check your pm's

 

Ditto on the 09/03 build date. I thought it was just coincidence. No flooding, good gas mileage;16-19.5 mixed until this tank. It's going to be under 14; when I actually took 10 mins out of the every morning to warm it up. I will resume with the 2 min warm-up next tank and hopefully go back to "normal"

 

what? the dealer said the mileage is bad because you haven't changed oil yet? if you speak to this guy again, tell him my 8 has had two oil changes already and it only has a little over 2200 miles. my last tank got 16 mpg, just a little less than my normal 17mpg. i'm the one changing my oil too because i've heard stories on this forum and it's easy enough to do it myself.

good luck and report back.

yamajj

 

I just filled up today 150 mi. /14.5 gal. I have let it warm up on these colder days. I have 7K miles on the car. All tsb's have been taken care of. I would be willing to try a new MAF. I can't think what else it could be. Its not a bad cat, that was replaced back in September. By the way, mine is a 9/03 build. Purchaced 06/04.

Also, my daily commute is 15 mi each way. 10 mi is expressway/tollway.

 

The gas mileage issue really is the bummer for me with the 8, an otherwise great car. I don't mind the lack of torque so much (made worse by the fact that I got the A/T, so I get what I deserve ) but I get like 12-13 MPG in the city and for weight of the car and the power of the engine, that's really weak.

 

It may, and it may not... I also have a 9/03 build. I'm just curious if his is a later build...

The tailpipe smoot has more to do with the rotary consuming oil in it's combustion cycle than running rich. I have seen a direct correlation between hard driving=>oil consumption=>extra smoot, and light driving=>low oil consumption=>light smoot. Much of the excess fuel is used to keep the cat cool.

 

Suburban driving is a better description- when I say city (the term the govt uses) I mean stop lights, changing gears, accelerations and decelerations- unlike highway with a constant speed/rpm.