Quote:
Originally Posted by tinduck
Maybe you are right, but in THEORY the warm-air-blower-through-the-lower-grill has some advantages over oil pan or cooling water heaters:
- behind the grill is the water cooler => gets heated. Heat transfer should be great, after all this is an air-water heat exchanger.
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The problem with blowing into the engine bay through the grill is just that: Most of the heat will be absorbed by the radiator, but the coolant in it won't warm the engine itself since the thermostat will be closed. Most of that heat in the radiator will be lost to the ambient air the minute you start driving. Of course, if the warm air is blowing all night, then once the radiator warms up the engine will start getting some heat. On the other hand, if the warm air is blowing all night, then it's not really warming a cold engine, but slowing the cooling of a hot engine after parking in the evening.
Still, any heat that gets into, and stays in, the engine is good.
Quote:
Originally Posted by JethroBodine
I remember reading about the dipstick type heaters not being recommended when they first came out, but not sure what the exact reasoning was.
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It's about the heat density, ie how much heat is emited per unit of surface area. I don't remember what the maximum limit is, but above that the oil starts to fry. A dipstick has very little surface area, so it would have to be very low power to be safe, but then it wouldn't do much.