You won't necessarily hear detonation at highway speeds, so no, I woudn't EVER use 87 octane. May be 89 around town, but on the highway, only 92.

As for compression heat, yes, the more you compress a gas, the more heat it will have -- plain law of thermodymanics (the energy has to go somewhere). The amount of waste heat an engine produces isn't the same subject -- that will be determined by efficency, load, and valve timing (along with a bunch of other stuff).

Duke:

The Alfa "hole in the piston" is indeed a flame propagation thing, determined by the factory. Apperantly it "blowtorched" rather nicely in high speed photography or something, I don't believe there is a thin spot or a ridge on the piston there. It's also repeatable, so must be something characteristic of that particular engine. Probably go something to do with swirl as that is a hemi with the spark plug pointing straight down in the center. Who knows. Certainly would ruin your day, anyway!

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!