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RX-8 Discussion General discussion about the RX-8 that doesn't fit in one of the specialty forums.

has anyone fixed their mpg problem.

Old 02-28-2009 | 08:25 PM
  #26  
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Is there possibly anything that we can learn from the 2009 update of the Renesis?
Old 02-28-2009 | 09:21 PM
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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.
Old 02-28-2009 | 09:26 PM
  #28  
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Originally Posted by John - 5x Racing


Brettus,
Did you lose power when you had the cpu flashed? And, where did you get in flashed at or what product are you using to flash it yourself? That is definitely a mpg increase, was it in addition to any intake/exhaust mods?

Thanks,
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 .
Old 02-28-2009 | 09:27 PM
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Originally Posted by 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.
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.
Old 02-28-2009 | 09:31 PM
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Originally Posted by 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.
oh trust me! i love it! lol.
Old 02-28-2009 | 10:27 PM
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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.
Old 02-28-2009 | 10:57 PM
  #32  
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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.
Old 02-28-2009 | 11:17 PM
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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.
Old 02-28-2009 | 11:18 PM
  #34  
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my mpg rose after i added air into my tires. so im now getting 17 but i used to get 14-15
Old 03-01-2009 | 01:25 AM
  #35  
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I'm at 190 miles to the tank and have to fill up soon..
Old 03-01-2009 | 01:40 AM
  #36  
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^ 270 miles here
Old 03-01-2009 | 03:49 AM
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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.
Old 03-01-2009 | 08:14 AM
  #38  
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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
Old 03-01-2009 | 11:37 AM
  #39  
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Originally Posted by Sean ***
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.
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
Old 03-01-2009 | 12:03 PM
  #40  
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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.
Old 03-01-2009 | 02:46 PM
  #41  
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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.
Old 03-01-2009 | 06:23 PM
  #42  
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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.
Old 03-02-2009 | 06:12 AM
  #43  
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Originally Posted by 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.

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
Old 03-02-2009 | 05:01 PM
  #44  
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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.
Old 03-02-2009 | 05:20 PM
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It could be worse, we average 6mpg, and our gallons are bigger than yours...
Old 03-02-2009 | 05:26 PM
  #46  
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Originally Posted by Sean ***
I don't want to hear about how your mpg sucks or how you can supposedly change it. I want to hear from people who have had an MPG problem with their 8 and actually fixed it. Driving another car does not count.
Yup. Get a Honda.
Old 03-03-2009 | 06:58 PM
  #47  
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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.
Old 03-05-2009 | 08:52 AM
  #48  
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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.
Old 03-05-2009 | 11:21 AM
  #49  
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Originally Posted by John - 5x Racing
Could the premix be helping to increase the mpg?
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.
Originally Posted by John - 5x Racing
When was the last new flash released from Mazda? I have an 07, surely there was one in between then and now. Also, has anyone had any experience with aftermarket flashes, like Racing Beat?

So far it doesn't sound like there is a lot that will improve the mileage on these cars, so it is a good challenge at least. It will be interesting to see what happens. I am looking forward to the simple easy things like lighter oil in the tranny and rear end, some cheap things might do the trick and it sounds like not many people have done it yet.

Thanks for all of the input, keep it coming.
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.
Old 03-05-2009 | 02:19 PM
  #50  
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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 ......

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