I apologize if this was previously discussed...

Correct me if I am wrong, but I believe the recommended fuel for the Mazda RX-8 (6-speed) is Premium, 89 octane?

Now is it harmful to run a higher octane? Is there any harm in running 93 octane?

 

There is no harm in running a higher octane. People here, with engines nearing or over 100k, have used everything from 87 to super premium without issues.

 

The recommended fuel is 91 or greater, not 89. That being said, people have ran 89 with no issue, you just may experience some small issues with it until the fuel trim gets used to it.

However, some IIRC have had issues with 89 to a greater extent. When in doubt, use 91-93. Using higher octane doesn't gain you any power benefit as people mythically believe. It just helps prevent knocking.

 

Thank you for the input. I have only owned my RX-8 for about 5 months, it is a 2005 6-speed. It had about 24,500 miles on it when I got it and I have been running 93 octane since I got the car.

 

QFT

 

91 at least totally!!!!

 

I SWEAR TO GOD that those Civics guy said it increases your hp by 10% or more !!!!

 

89 is not premium

 

I bet some sheeple out there have just used 87 every time and never even popped the hood. Im sure that's happend.

 

I figured there isn't that much difference in gasoline brands, but i get better performance out of Shell premium every time.

 

Shell gives me best performance, but it also the least MPG (maybe my foot gets heavier with Shell?)

Mobil gives me beset MPG, but not performance

BP suck in both mpg and performance.

 

I think it depends on where you live. If you're in a cool climate, 91 may be okay for you - in a hotter climate you might need to use 93 in summer - or even all year round.

 

I would buy 91 more if I could but fact of the matter is up here all I get most of the time offered is the typical 3: 87, 89 & 93. Just more money outa mah pocket

 

Wait, is my E85 not good enough?

lol but whatever octane premium you get will be fine. A little premix doesn't hurt either.

 

I agree, shell sucks for MPG (even when driving "slow") but does give great performance. Same thoughts on BP but I have never tried Mobil. I've never come across anything that gives the best of both worlds. Has there been a "which gas poll" yet to get a bigger picture of people's experiences?

 

I tried using 93 in my car for the first time recently and it did not like it at all - it seriously degraded the accelerating power. I went back to 91 and it runs like a charm again.

 

You probably got bad gas ............ the octane rating wont do that .