DAC17

Is there possibly anything that we can learn from the 2009 update of the Renesis?

BLIPY

WOW! it looks like everyone has good mpg. i only get 13! if im lucky 14-15 has been the max.

oh btw. im blipy and i just got my 8 a month ago. 06 mt and i just put in a mazdaspeed cai.

Brettus

iTrader: (2)

hell no - gained about 15-20 hp
was using a piggyback - now use hymee protuner .
I did have other mods but found no improvement till i did the tune .

The ecu will adjust your afrs for most mods you do so you will end up with the same mpg with or without them .

Marklar

I get the same MPG with city driving. It has more to do with driving style and the type of driving than with the actual car, I think. Use a lot of right foot and shift late and you won't get the best MPG, but you and your car will love it.

BLIPY

oh trust me! i love it! lol.

Low Fly'n 8

I have gotten a consistant average of 20 mpg since new. 04 MT daily driver with reman engine at 69K and now at 78K. I use Luas UCL and 93 Amocco Gold. Fresh Castrol GTX 5W-20 every 3K. Racing Beat exhaust and K&N drop in filter since new. Tire pressure @ 32 psi and rotated every 5K. Redlined every day and shift normally around 5K. It works for me.

mikeyfuzz

I get **** for mileage, I don't drive it super hard, with 50/50%, city/highway driving and my last tank averaged out to 12.5 mpg. It had been going down for a while and I'm getting a little worried at this point.

Icemark

I remember recently on a Speed Channel show, they did a test with minor and minor changes on a newer Dodge V8 and a Toyota Camry V6 99% of the changes did nothing to increase gas mileage. These were changes like headers, intake, exhaust... everything you could think of.

In fact the only noticeable improvement in mileage was increasing the air in the tires to 50 PSI.

HWK11

iTrader: (2)

my mpg rose after i added air into my tires. so im now getting 17 but i used to get 14-15

RotaryP7

I'm at 190 miles to the tank and have to fill up soon..

cjkim

^ 270 miles here

Sean Cox

for those of you talking about the thread title "has anyone fixed their mpg problem" being general talking about all rx8s: getting 18 mpg is not a problem! I was referring to thoes of us that were getting 12 or less driving normally not auto crossing. Not ALL RX8s im looking for help and ideas not "it gets 16mpg its how it was designed"

stuff that has seemed helpful:
-spark plugs
-redlining
-coil packs
-ecu flash

Thanks for thoes of you who have helped ill be checking some of this stuff this week.

TOMCATS8

iTrader: (1)

I notice now that it's getting warmer I'm getting better mpg. I bought my Rex Dec 08 (05 mt). Around that time it was averaging btw 11-13 in 17-24 degree weather.

Now I'm averaging 16-17 in 37-54 degree weather..

Also I used to warm up my car for at least 10 minutes, but thanks to this site, I quickly drop that idea and warm it up for 2-3 minutes, then keep it near 3000rpm till it reach normal operating temps...

Also maxing out 2nd and maybe 3rd merginging on the highway helps... LOL

cjkim

while you're at it
clean MAF
throttle body

12 mpg is not surprising depending on how you drive/conditions.
if it's 100% city with 10 minute trips, 12 doesn't sound all too abnormal

mikeyfuzz

Heres my feelings on fuel mileage. First off, I love my car and wouldn't trade it for the world. We own sports cars and we shouldn't expect great mileage, but shouldn't we still push our vehicles to get the best mileage we can. Isn't technology advanced enough that we can improve mileage without sacrificing power, or increasing power without decimating mileage.

If my car is stuck at 13 mpg, fine. But don't flame me cause I ask others, who get more like 17-18, what I can do to get my mileage up.

Sean Cox

thanks mike! I knew what i was getting into when i got the car. I used my FD for a while before it broke and I was getting 14 mpg on that one. my driving style has gotten more conservative since the FD. Im still keeping the car if I get ten mpg, Ill just have to ride my bike more LOL.

mmats69

didn't know there was a "problem" with the gas mileage. if i drove a lot in town, short trips, I got about 13. out on the highway b/t 20-25.

John - 5x Racing

This is the exact reason why I am doing a mpg project/experiment with the RX8, not to make the car get 30+ mpg, which is not going to happen, but to see what actually works in increasing mpg. So far from the experiences of the members of this thread, it seems that most common way to increase mpg's is to drive more conservatively, which is hard to do with this car. If I could afford a ton of dyno time I would test each mod for horsepower too, this would certainly interest everyone that is not concerned about getting better mpg. I just might dyno test a Green Performance Air filter against a stock one, this is the easiest mod in the book and from reading about other tests it was said to gain 5 hp. Of course if I got some manufacturers to sponsor the project I would definitely do dyno testing...

Still looking for past experiences with gains or losses on parts that were intended to increase mileage, I will post them on the page:
http://5xracing.com/p-1057-mazdarx8projectmpg.html

Georgia8er

Driving "conservatively" won't get you much of an increase, unless you're driving like a bat out of hell all the time otherwise. My experience is minimizing the time you spend idling and city type driving will do more than anything else. Overall I get the same fuel economy if I push it hard and do a 1-2-6 shift (since by the time I max out 2nd I am going over the speed limit) than if I go easy and go through the gears.

Most mods that can be done to this car have been dyno tested, just search a little and you'll find what you want.

PhillipM

It could be worse, we average 6mpg, and our gallons are bigger than yours...

DOMINION

Yup. Get a Honda.

Raptor75

I hear and feel your pain, when I bought the car I was expecting 15 MPG in the city what I got was 11 to 12MPG city in Chicago. I spent years trying to figure out why the MPG was so poor. Had it to the dealer several times, no help. Changed filters, over inflated tires, went to synthetic oil, ect... nothing helped.

As I owned the car I finally realized that the great mileage some report in all likelihood happens on far less congested roads then the ones I drive. I have a lot of stop lights and idea time which kills the MPG. On the highway I have hit 22MPG doing 70MPH and am sure with cruse control and a lower speed could hit 24MPG.

So this leaves me with the simple fact that the RX-8 is a gas hog. The RX-8 gets close to 15 to 20% worst mileage than a comparable piston car by its nature and there is really nothing we can do about it.

Well almost nothing, the only thing which helped me get better mileage was a Scanalyzer. This device would feed me information on my current fuel consumption and trained me to get better mileage by driving more gently. I found I was getting between 1 and 2 MPG better when I used it. Unfortunately the car was no were near as fun to drive doing this.

I wish you the best and feel your pain.

mikeyfuzz

To get back on Topic. I have only been getting 12-13 mpg for the last few fill ups. When I first got the car, I was going 190-210 miles on a tank and my commute hasn't changed. I just put in a new air filter last fill up and it has more power but it didn't seem to help me on mileage. I have an oil change coming up so I might ask the Mazda guys about plugs.

robrecht

Some have reported better mileage with premix. I didn't see any improvement but don't have long-term data for no premix and my mileage was never problematic. I average 19 mpg with almost no city and almost no highway miles and lots of red-lining. I have a near perfect back road 'mountain' commute. With very conservative 65-mpg highway driving, the best I've seen is 26-28 mpg and someone else here reported 29 mpg IIRC.
The most recent flash is MSP16 from March of 2008. Racing Beat said they were not ablle to improve fuel economy with their flash but others have with custom flashes designed and tweaked for their individual car. That's not cheap so it's hardly worth doing as a fuel economy mod and leaning out your AFRs will likely shorten your cat life if ou still have one. The stock coils are prone to failure and some have reported improved fuel economy (2-3 mpg or even more) by replacing or upgrading their coils.

Good luck with your research, but I think it will be difficult to prove anything without lots of long-term data to balance out all the variables.

Brettus

iTrader: (2)

Driving under 3700 rpm while on cruise will definately help with mileage .
I have some great dudelogger logs that demonstrate how afrs drop to 12-13:1 down from 14-15:1 . A 10-15% reduction in fuel just by going a few mph slower ......