I did a couple of cross-country trips in the last three years. I agree with those who say that the octane of the gas available has to do with elevation. Anytime I was in areas out west that were up in the air a bit, the octane of the gas was down several points. I had no trouble running that gas as the air is less dense and you are less likely to run into trouble with detonation, etc. The car (not my Challenger, BTW) was noticeably slower, though. Not due to the gas - due to the air. Now that I think of it, I was slower, too!