Quote:
Originally Posted by Daox
I would imagine the mileage difference is mainly during the warm up period. After that, I can actually see the now 'cooler' hurting things. If the oil can't get as warm as before, it will actually keep the oil slightly thicker. Great if you have short trips, maybe not as great if you typically have long trips?
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Probably depends on how much of an effect the thing has on oil temps once everything is warmed up. Oil is not great at transferring heat, so things like oil coolers need to see a big temperature delta to be effective.
Google tells me that the ideal coolant temperature is 195-220°F. Oil is also pretty happy at that temperature range -- it's driving out any water and fuel dilution, but not hot enough for the additives to break down yet.
I think the concern in your post loops back around to the usefulness of checking the oil pressure. If the car spec'd 0W20 originally, but you find that there is plenty of oil pressure even on hot highway runs, you could experiment with 0W16.
