From 1st year college chemistry, one pound of gasoline will combine
with 3 1/2 lbs of oxygen (about 15 lbs of air) to give 3 lbs of CO2
and 1 1/2 lbs of water.  Some of that water (and CO2) will find its
way into the crankcase, where the dew point of the water vapor will be
about 180 degF.  On shutdown the water vapor will condense on the
cooling surfaces to make corrosion-causing acids.

Car engines flush the crankcase with positive crankcase ventilation.
That is thought to explain the considerably longer engine lives of
cars. Some are now suggesting a ground based dry flush system for
aircraft engines, but unless it is immediately applied on shutdown,
I'd think the value would be limited.  A saving grace for cold engines
is that all chemical reaction rates (including corrosion) are cut in
half for every 18 degreesF of temperature reduction.
--- SBBSecho 2.12-Win32