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Old 07-13-2003, 07:31 PM
Arthur Dalton Arthur Dalton is offline
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Join Date: Aug 1999
Location: Florida / N.H.
Posts: 8,784
As a general rule, as compression/ compression ratio goes up, the plug temperature goes down. A cold plug is more easily fouled than a hot plug.

So, ... a high hour engine can benefit from a heat jump as , not only has its compression weakened, but a hotter plug will foul less from oil deposits common on h/h engines, [ burns them off better].
On newer lean burn engines. I would prefer oem spec...
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