Quote:
Originally Posted by Gforce
The knock sensors don't care. They have no moving parts. What may matter is borderline detonation which knock sensors have to permit in order to have sometung to sense.
Road engine manufacturers select the compression ratio primarily for the fuel they expect their customers to agree to pay for. In North America most customers won't pay for anything but regular which is 87. In Europe the lowest octane you can normally buy is 91, that's their regular. Their premium is 95 generally.
Only high compression using high octane fuel delivers best fuel economy. Compression ratio is selected first for fuel price in North America, not fuel economy.
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They have exactly the same as we do and just their numbers are higher since they rate on a different system. Their 91 is actually the same as or 87. It has nothing to do with them being willing to buy higher levels.