A 48 Chevy had something less than 7:1 Compression Ratio and it ran great on the stuff. There was leaded gas back as far as I can remember, back into the fifties.

Phillips 66 got it's name very early. My Dad said that he remembered their ads indicating that they guaranteed 66 octane. I think that was probably in the early thirties.

Compression ratios were on the rise all through the fifties and sixties, probably peaking out in the late sixties, early seventies. Of course in 72 they all went to hell with the unleaded fuel trend starting to be pressed. By the sixties, regular was higher octane than today's Premium.

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2001 SLK 320 six speed manual
2014 Porsche Cayenne six speed manual

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