Ok, stupid question. I was at the gas station and some guy was putting in 91 in his RX-8. I know in my NA, i ONLY ran 87, anything more was a waste of money. Does Mazda recommend 91 or was this guy just being an idiot?

Mazda reccomends 91 octane for the rx8

Mazda recommends is but is not required, the manual says that reduced performance will result from using lower octane.



The RX-8's ECU advances ignition timing agressively, that's the reason for using high octane. If lower octane is used the timing will be less agressive resulting in less power.

I always use 91 too...

and will slightly increase the chance of detonation!

Sorry, i just hit reply and it came out like that...



I wouldn't worry about detonation in the RX-8, the ECU is super smart and will retard timing at the slightest hint of detonation. There are a lot of people in the rx8club forums that run 87 octane with no problems at all.

you kidding? i've talked to lots of rx8 guys that ping their motors left and right. the ecu is good, but it's not THAT good. the apex seals are just more resistant to detonation than the old ones.

One of the things I heard (and read some time long ago) is even if your ECU can keep up with detonation, and the 8's is pretty good, you will give up some power and thus some MPG. (as if tracking mpg in an RX8 is a practical thing to do!) https://www.nopistons.com/forums/pub...1047683785.gif



My 8 (the one my wife let's me use sometimes) lives on 91, not willing to scrimp pennies for potential power loss or worse, hidden mystery damage later. https://www.nopistons.com/forums/pub...1047683664.gif



I say this as an owner, not just cause I work at Mazda.



Neil

actually, the lower the octane, the more power it'll make under a given set of conditions (of course staying away from the detonation threshhold). but the rx8's ecu is all nutty, so that might not be applicable.



i run my fd on 87 octane at 8psi ~300-310 whp. and i don't have a hint of detonation. $.20 a gallon savings on gas is nice.

the rx8 we play with gets 91 when it goes to the track, but otherwise it gets 89ish. 22-23mpg highway....



mazda rotaries are kinda funny like that.



the fd has 3x the power and 2x the milage of a 73 rx2, but reliability is the same.