"Dennis O'Connor" wrote in message
...
John, that has been the point I have been beating on... A quick preheat
does
nothing, except convince the pilot he is being good to the engine...

A thorough preheat of a number of hours, with adequate insulation and
keeping the wind off the prop blades, does bring the engine core
temperature
up, and certainly does no harm...

Leaving heat on the engine all the time may set you up for condensation
rusting - depends on the details...

Yes...unless you use both a cylinder AND an oil sump heater.

http://www.reiffpreheat.com/FAQ.htm#QA3