Just got my 8, it is alot of fun. Other than performance issues, is there any problem with using the 89 octane? I am sure this was discussed before but I couldn't find it.

I used 87 octane today. I got used to using it on my old car and I used it on this. I totally forgot about it. Oh well.

I tried two tanks of 87 instead of 91 that I had been religiously using prior. In both tanks, I've gotten 30+ miles more per tank with no other changes other than fuel grade.

I have used 87 octane for 4 months now - no loss of performance, and better gas mileage for me as well.

my dealer told me not to put any octane under 92 in the car. they said anything under 92 will hurt the internals. i think its also in the manual but i'm not sure

According to the owners manual that I downloaded from the mazda site it says that "you may use a regular unleaded fuel with Octane Rating from 87 to 90 (91 to 95 RON) but this will slightly reduce performance." (Qoute from "Fuel Requirements" Page 4-2)

I have been using 89 in mine for quite a while and have not noticed any differences in performance so unless you are going to the track I really wouldn't think that it makes a difference. Just my thoughts.
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I have been running 87 for a while now and the only thing I noticed as a difference from 93 was a poor idle. I can definitly tell when the rest of the 87 is out when I fill up with 93 cause the idle smooths out and vice versa. No performance loss though. I am sure once I start doing mods (canzoomer, midpipe/cat, possible exhaust) I will definitly use 93 all the time.

Originally posted by JasonHamilton
I tried two tanks of 87 instead of 91 that I had been religiously using prior. In both tanks, I've gotten 30+ miles more per tank with no other changes other than fuel grade.

I'm kinda slow,JH-you get better mileage with 87 ??

I've noticed NO difference between using 87, 89, 91, or 93 octane with the same driving habits, in terms of gas mileage or performance. I have had the car for a year now.

Has any on the board tested the VP racing 100 octane? I am supposed to have my Velocity Red this Monday and I was thinking of doing some tests with 87 vs 100 and see what differences I see. Anyone done this yet?

i have tried 89 and 91 but not 87 yet. cant see much difference between 89 and 91.

Originally posted by Seenitall
I'm kinda slow,JH-you get better mileage with 87 ??

Yes. Instead of 200-230 per tank, I'm getting 230-250 range.

Originally posted by JasonHamilton
Yes. Instead of 200-230 per tank, I'm getting 230-250 range.

JH thankx:)

I see no diffrence or feel no diffrence between 87 or 91, I do see I am saving about $3 per fill up though.

Your car should get better gas mileage on a lower octance fuel. Higher octane does not mean more power, it just means that it takes more heat to ignite the fuel. The obly problem with the lower octance fuel is that they preignite easier than higher octane fuels.
Higer octane does not clean your engine. And the only way you'll get more power is if your engine can be tuned to take advantage of it. The RX-8 may automatically adjust it "timing" to protect against damaging pre-ign, which is why it would make less power with the lower grade.