[masraum]

Originally Posted by Nostril Cheese

Some of my Subaru friends tested this a few years back (serious turbo guys with dynos). My understanding from them is standard Subaru ECUs will not advance timing to take advantage of higher octane fuel. They will only retard timing if detonation is detected. No appreciable HP or MPG gains. These guys build stupid fast machines... but they sound like broken flat fours...

Of course, you could always install software to take advantage of the timing. You would then need to run high octane at all times.

I don't think ethanol is an issue with newer cars (you just bought a new one, right?).

My DD is an E46 wagon that specs use of 92 octane. I've run it a couple times on 87 (like when 92 wasn't available). There is a noticeable difference in power and also less MPG.

Our Subaru is a flat-6 with no turbo. I wouldn't expect much out of a chip/tune for a non-turbo, and the missus is probably not interested in any weirdness that would probably come from a chip/tune.

On a turbo, I could see some possible benefit (probably requiring a tune). Turbo folks seem to love ethanol.

I have to say, I am loving the 6 cyl (vs 4cyl or now 4cyl turbo). We also seem to be getting about 28-30 mpg on the highway.