Quote:
mvd said:
"Shadetree mechanic" Good one!

We are talking about two different things as I misread your post to suggest that altitude causes the fuel's octane to decrease ("At higher altitudes with thinner air, the octane ratings AVAILABLE decrease proportionately"). Obviously, the fuel's the same and there's no change in it's octane rating. Sorry for the misread.

What I think you were trying to say (and your google post confirms) is that the octane required to prevent knocking decreases as the elevation increases (excluding, of course, turbos and blowers). Agreed?

Now back to my shadetree, Dave



Yep, you misunderstood me at first, and yes, the altitude changes the car's needs, not the fuel itself.. Even turbo and supercharged cars are affected I believe, as full-boost in high altitude is still leaner than low..., as the max boost is usually cfm-limited.. I think??

Somebody with more technical knowhow can elaborate, as I'm dipping my toes into speculative waters I don't really swim in..