The following is data I posted ont he 87 Octane thread.

While we were getting 18.5-20 in 8 and 20.5 to 21.5 in the other, I like many are looking to improve mileage, hopefully without any change in performance.

Some are experimenting with 87 Octane, I chose to try 89.

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We have been running 93 Octane because 91 was so hard to find. Based on this thread, I put 89 Octane in my wife's RX-8 to see if there were any differences in performance. First, we live at sea level, (Tampa FL), the temp was 84 today and a little humid. I put 14.2 gallons in so any remaining 93 Octane gas was significantly deluted.

I ran it on the interstate first and noted a some sluggishness for the first 5 miles or so.... or so I thought. After that, it seemed to run very will. I especially noticed good acelleration in 2nd and 3rd up through 6500RPM. I also jumped on it and hit 100 in 5th.

At present we have 80 miles on the tank and I got 68 out of the first quarter tank based on the guage. In comparing this to my RX-8, it seems to be getting as good or better gas mileage.

I will post data when we fill up. I know that some are using 87 Octane, I just thought it would be a less risky approach.

Lastly, please note that I am doing this to my wife's 8 so I cannot keep exact data on mileage cause she drives completely different from me. She runs in 3rd and 4th much longer than I do.

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89 OCTANE Update

No loss in performance... just when past 160 miles on first half of the tank. This is about 10-20 miles more than we normally get on the first half of the tank. If this continues, I expect to pull approximately 300 on this tank. From half to on quarter seems to last a while and then it drops like a rock the last quarter.

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I should have data on the MPG for the first tank of 87 today.

My results as of late. 330+ ?? Hard to believe.


Mileage Gallons $/gal Total m/gal Trip
309 13.447 $1.719 $23.12 16.81 226
569 14.235 $1.699 $24.19 18.26 260
800 14.216 $1.799 $25.57 16.25 231
999 12.538 $1.699 $21.30 15.87 199
1207 13.727 $1.719 $23.60 15.15 208
1435 13.001 $1.669 $21.70 17.53 228
1698 13.119 $1.639 $21.50 20.06 263
1968 13.815 $1.699 $23.47 19.54 270
2214 12.797 $1.733 $22.18 19.22 246
2485 14.079 $1.519 $21.39 19.25 271
2740 13.900 $1.589 $22.09 18.35 255
3001 13.449 $1.649 $22.18 19.41 261
3289 14.422 $1.559 $22.48 19.97 288
3557 14.404 $1.599 $23.03 18.61 268
3838 14.287 $1.499 $21.42 19.67 281
4041 13.202 $1.519 $20.05 15.38 203
4245 10.417 $1.579 $16.45 19.58 204
4455 10.769 $1.579 $17.00 19.50 210
4695 12.008 $1.499 $18.00 19.99 240
4903 13.700 $1.459 $19.99 15.18 208
5154 12.973 $1.449 $18.80 19.35 251
5406 12.990 $1.499 $19.47 19.40 252
5712 15.001 $1.419 $21.29 20.40 306
5950 11.863 $1.459 $17.31 20.06 238
6208 13.243 $1.359 $18.00 19.48 258
6459 12.841 $1.479 $18.99 19.55 251
6718 14.003 $1.499 $20.99 18.50 259

Believe it.

I think it would be interesting to build a matrix listing mileage by state/region and octane used. I have been doing some reading, and I wander if the "reformulated" gas sold in CA and a section of the northeast may be the problem. Also those using corn gas may want to provide data. Just a though...

oh my friggin god... you guys are getting over 300 miles on a tank
!!!! what the hoochies!!! im in 6th gear by 50 mph. shifting like a mo'f#ing grandma happy to break 220 miles on a tank..... im pissed.

My last few tanks have been surprisingly bad. So much so that I'm now trying to see if shifting at 3k RPM will make a difference. I was averaging about 240-260 before the light came on when I wasn't running the AC. My last tank, I ran the AC and got 220.

So far I've only been above 3000 when absolutely necessary and when in 6th gear, going 80 or so down the highway (texas traffic is like that). I probably average about 60/40 highway/city. We'll see how it goes.

Most of the tanks of gas I've run were 93 octane. This one is 89. The best tank I've had was 318 on amoco ultimate(93) on a 90/10 stretch of city highway. I actually seem to get the best mileage out of Amoco gas and the worst mileage out of Shell gas (strange to me as I've always bought shell/texaco). Anyway, this tank is chevron and I currently have about 70 miles on it and i'm still just above 1/4 mark on the gauge, however we know how accurate this gauge is.

I get about 200-215 out of tank but mostly city driving. Maybe 5% on the highway. Looking forward to driving to Alabama in October to see what I get on the highway.

I think if you shift too early you'd end up burning more gas to get to the speed you want. It is like you are trying to reach 70 from 40 in 6th rather than up to 60 in 5th and then to 70 in 6th. I believe the former would take more gas. Or am I wrong? Please conrrect me if I am wrong.

Mileage continues to improve
 

Well folks, my wife and I are amazed to see that our mileage is creeping UP!!!

We are both getting 21 MPG. Both cars have over 14000 miles and the improvement seemed to start around 12000 miles.

Of note, we are both mixing 89 and 93 octane to get an average of 91.... or as close as we can.

I have a Canzoomer Stage One on order so that will be interesting to compare with my wife's car which we plan to keep stock.

Thanks

With the stereo cranked, it's so smooth that I end up shifting out of 1st and 2nd around 6000; but for better mileage, I'm going to try taking the lead out a little and shift around 4000.

Of course, slow vehicles beware because I do DOWNSHIFT!

My 8 has been pretty consistant at doing 230 - 240 miles before the low fuel light turns on.

But I'd guess about 80% of my driving is city, and it's always with AC on.

I usually get 300KM not miles So about 187 miles...God to get 480 km would be almost as good as ***

well, i know my last 2 tanks were bad because i did a few very high speed (120+) trips up the highway just because I could. No racing, but high speed driving late at night is kinda fun and a gas killer.

Worst for me was when I first got my Rx8 (after the initial break-in period) - I consistently averaged between 200-220 miles per tank regardless of driving style

Now my gas light comes on at 220ish and I usually fill up at 250 (using between 13.5 - 13.9 gallons).

My best mileage was on a road trip down to LA not too long ago. I averaged between 260 - 290 miles per tank, and that was with going 90+ on hwy 5.

In general, I'm a spirited driver, so I really don't mind the 220-240 I average.

hey it seems that cruise on highways at or under 3750 rpm and shifting under that same rpm in city driving is the way to break that 19~20 mpg barrier. But has anyone considered load vs rpm? How does rotories react to heavy load (lower rpm) driving?

My worst tank of all around town driving is about 220 miles and the lite comes on needing about 13.5 gals (about 16.5 mpg). The last two tanks all hwy 371 and 375 (about 27.5 mpg) thats with cruz on and being good at 65mph, but its no fun and hard to do. I normaly get 23-24 mpg on hwy no cruz having some fun. I use 87oct on freeway where I'm cruzing and when I'm gona have some fun around town I use 91oct.....what a fun car

I am on my first tank of gas since I bought my car, and the light came on at 235 miles. Have you guys notest the mph getting better as you get more miles? What Octane have you guys been using and where do you get it from?
Rx-8, 350 miles so fare, I am in texas and have been using the S**t out of the ac.

Sup Ya'll - I have been monitoring this board for several weeks now. I love the 8, but the potential gas mileage issues seriously scare me. There seems to be no reason why some owners get relatively good mileage 18+, and others get 12-13 MPG. With gas prices at $2.50 per gallon, and going up, I question the wisdom of purchasing a car that may get such poor mileage. Some of you getting 180 miles per tank is insane. How do you tell if you are getting a "good one" just by a test drive? I am also considering a WRX (performance very close) but it's butt ugly when compared to the 8 IMO (no offense intended to WRX owners - great car). Then I read senior members here trading in their 8's and getting killed on depreciation$ Perhaps the 05 turbo Legacy? What the f^*k to do?

13.5 gallons per fill up usually gets me a bit over 200 miles. That is 100% city driving and the majority of my trips are under ten minutes.

Seems to be getting better
 

301.5 / 14.33....

21+MPG

Would have been better but I caught myself cruising in 5th a lot at 65 after coming out of a construction zone.... just not paying attention.

Holy cow! 350+ MIILES on a friggin tank. I would poop all over myself if i got over 250+ on a tank.. my best tank of gas to date... from a completely full - top'd off tank to driving way into the orange gas light has been 211 miles. yielding me a unimpressive 15 mpg... thats at best.. and that was on a road trip from dallas to austin. which was 100% highway..... and still not over 15 mpg.. HOW DO YOU DO IT?!?!?! someone tell me the secrets to achieving higher gas mileage. where are your shifting points. i shift between 3k and 3.5 k
.. i did find however 87 octane gets me around 200-210 on a tank.. 91 octane gets me 160-175... lower octane = higer mileage. anyone else?

mine was 225 evry time the light came on .now im getting 260 by disabiling the TCS/DSC. my drive consist of city drive 80%of the time speed limit is 45 but in city drive it alot of stop and go.i would love too see even close too 300mpg but if i have too give up hp then i'll stick too 260 and be happy

400 km on my last tankfull of premium. That's about 250 miles. But I was doing the engine break-in so I basically taking it real easy.

Finished engine break-in so now driving the car harder. We'll see how much fuel economy suffers.

Three tanks burned through now, and consistently getting around 16.7 - 17.9 mpg. Mixed driving, rural roads, no real open highway, occasional redlining.

That carries me for about 200-230 miles before I'm looking to feed again (1/8 tank or so left, but no warning light yet, so I could probably push my luck to 250 or so).

Mileage is up to 21.26.

301/14.15

Regularly get 290-300 per tank


My stage one sytem just came in. I will install and resport mileage after system stablizes.