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...

My experience has been that with semisynthetic, multiviscosity oils
preheating is not necessary - until you reach arctic conditions..
denny

"John Galban" wrote in The reason for the Alaskan
habit is that when temps go low enough, a
chunk of frozen oil can develop in the crankcase. Even after
preheating the engine to what seems to be a suitable temp, you can
have a frozen chunk of oil surrounded by slightly warmer liquid oil.
(PA28-180)