Ah, Eugene; yes, 30 cents a gallon sounds very small, but when amortized out over 20 years and 200k miles you'll save over $3000. My 20-year-old car is now worth maybe $3000; so, I have a free S-class Mercedes to drive for the next few years. Maybe old Ben Franklin was on to something.

Gas prices are an emotional thing; folks will drive all over to save a nickel per gallon, then walk out of the house and leave 50 lights on.

But, I do agree that if you plan to run her a bit hard in hot weather, then the possibility of High-RPM knock is there. The one and only time I ever heard knock on 87 octane was one very hot day when pulling past 5000 RPM on an incline. Haven't had the occasion to do that again in the last ten years or so.

DG