Preheating engines: Airplane engines versus auto engines

On Wed, 19 Dec 2007 17:35:50 +0000 (UTC),
(Paul Tomblin) wrote:

In a previous article, "Peter R." said:
Why is it that here in the Northeast US seemingly no one preheats their
automobile engine before start-up in very cold temperatures? Is the long-term
damage the same for both autos and aircraft engines? If so, why do you
suppose auto owners don't typically do this? Is it because that most auto
owners do not keep their cars very long?



Aircraft engines are air cooled, auto engines are liquid cooled.

The following is what I was told when I was driving a Volkswagen Beetle,
and the experts were saying that you needed to let the beast idle for at
least 5 minutes in the winter:

Liquid cooled engines stay in a very narrow temperature range while
operating, so are built with very tight tolerances, but air cooled engines

Careful here. Don't confuse tight tolerances with tight clearances.
Aircraft engines have tighter tolerances than automobile engines.
Automobile engines have tighter clearances, but wider tolerances than
aircraft engines. If my car engine had the same fit as my IO-470N
it'd be considered worn out.

Roger (K8RI)
have more slop because they get both hotter and colder than liquid cooled
engines. Also, they are cooled primarily by the engine oil. Because of
that, you need to preheat the engine enough that the oil is spread around
and everything has warmed enough that the pistons are making good contact
with the cylinder walls.