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KingZarkon t1_jdzwod4 wrote

>Has nothing to do with wear. Leaded fuel has a very high autoignition point that prevents knock. Modern fuel uses alcohol, but engines designed for alcohol free fuel are dangerously unreliable.

Turns out, it does both, actually.

>Lead allowed the development of higher 'octane number' fuel (the higher the number, the greater the resistance of the fuel to uncontrolled burning in the engine, or 'detonation'), and was also discovered, later, to have the property of protecting valve seats from wear.

Source

As for knock, you could just go all the way. E85, for instance, doesn't detonate, period. You can run the timing all the way to TDC and be fine. Would need bigger fuel tanks, though, so that might cut into payload a bit.

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