<<I hold that if you routinely run your engine (every couple weeks) and get
your oil temp to over 200 degrees for a few minutes during your run, then
you won’t have any water in your oil to corrode.  This is also drastically
affected by where your plane is stored.>>

I'll add my opinion here.  Yes, running the oil hot enough to drive out most
of the water helps, but remember that the crankcase is full of blow-by and
blow-by is essentially exhaust gas, containing maybe 10% water vapor.  So
there is no way to "drive out" all the water vapor in the crankcase.  Short
of pumping dry air into the crankcase (nitrogen would be better!) after
shutting the engine off it must be assumed that the engine will start
corroding as soon as it is shut off.  Corrosion goes faster at higher
temperatures similar to all chemical reactions so the best way to slow the
corrosion rate is to keep it cold.  Also, as was pointed out on this list,
most heaters only heat part of the engine, evaporating water from that area
which then condenses in other areas, creating a higher local water
concentration and speeding up the corrosion process.

My solution was to only heat the engine just before flight.  To do that for
little money I bought a kerosene "Salamander" heater and added some rigid
ducting to the outlet that aimed at one of the cooling outlets - no need to
pump air in both.  For safety I used about 5 feet of ducting to isolate the
aircraft from the flame and I started the heater before bringing it close to
the plane.  I have seen some people go to the trouble of pumping air in the
inlets, but that is a waste of time - the engine heats just as well with air
going in the bottom.  By the time I loaded and preflighted the airplane
(except for draining fuel!) the cylinders were warm to the touch and ready
to go.

Another comment - I don't see any rational reason why starting a cold engine
causes "excess" wear.  Oil will flow even when cold, except progressively
less so.  With the weak battery and starters in aircraft if the starter will
turn the engine it will usually start and run.  As it gets colder priming is
more of a problem and done wrong the excess fuel will wash the oil off the
cylinders, not a good thing.  If there is a wear problem starting engines
cold that is it and I think that is the main reason rental outfits will
require preheat when cold.  I found that with 20W-50 oil the engine would
start reliably down to 20 F and Below that priming difficulties and no
cranking speed made heating necessary.  With that criteria all engines I ran
went over TBO.  3 data points.

Gary Casey
Always ran Lycoming engines