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Old 11-20-2012, 08:47 PM   #86 (permalink)
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Originally Posted by Old Mechanic View Post
If I coast (engine on) it takes slightly longer for the engine to warm up, but I am getting better mileage since the available waste heat is lower.

Intuitively this is right, the heat rejection rate doesn't go down that much after it's warm anyways since the flame temperature and exhaust temperature are much, much higher than coolant temperature.

But what about lubrication? My engine makes groaning sounds when it's cold that go away when the oil warms up...very disconcerting :/ Wasting a bit of gas at low load letting the engine warm up faster makes me feel better about my bearings. Maybe I just need a 5W-20 instead of a 10W-30.
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