Originally Posted by nti_hazard88
In theory doesn't oil only deteriorate faster when the engine is "hotter"?
In theory, and in practice too I guess, a car standing has significantly poorer cooling capability than a car that's moving. Natural convection (or forced convection by the fans when they turn on) has significantly lower heat transfer capability than the type of force convection the car gets when it's going 40 mph down the street. So a moving car is able to cool your coolant significantly better than a non-moving car, resulting in a lower coolant temperature, if the engine in both cases are generating the same amount of heat. But obviously, a moving car generates more heat than a non-moving car. So, exactly which is worse for the car? Who knows. But I'm guessing if you're just cruising down the street a moderate RPM, the cooling advantage is not yet all eaten up by the increase in heat generation by the engine. If you're going down your favorite track full throttle, on the other hand, I'm sure the heat generated by the engine is now even or surpassing the cooling advantage.