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Old 10-08-2012, 09:29 AM   #186 (permalink)
pete c
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Originally Posted by tinduck View Post
I have yet to see a car which uses less fuel when cruising at higher RPM. Internal engine friction and pumping losses wil see to that!
This is more or less true, but, there may be cases where you are getting down close to lugging with your foot into it, where going a gear lower results in getting the engine up into a more efficient rpm range. I believe this is particularly true with diesels where the pumping loss advantage of having a wide open throttle is not a factor, but having it floored results in a much richer mixture. I had this explained to me by an old OTR driver with a few million miles of driving diesel trucks over mountain passes.
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