[turbocarrera]

We use (RON + MON)/2 and premium is 94 octane. I don't think 10% has any appreciable effect but I've heard that E85 definitely will.

I use it because it resists detonation and burns cleaner. I just did a valve adjustment before winter storage and I was kind of shocked to see how clean the backs of the valves looked - like brand new. Even the piston tops were pretty clean - a darkbrownish oily colour instead of the blackened carbon look I was expecting to see on 120k mile pistons. Mileage takes a little hit.