The biggest problem with running a cool engine is moisture and you will start sludging the engine up. Most of these trucks they are our toys so they don't get a lot of miles on them to get the contaminants out especially those of us that live in areas that can go from 40 to 100deg in the summer w/100% humidity and 40 to -30deg in the winter, condensation will get in the engine just sitting in the garage for 4 or 5 months. You guys in the desert don't have these problems but up north there are times when we will go out to the garage and the floor will be wet from the humidity and the engine will cover with moisture which also plays hell on aluminum parts. The oil should be changed before you put it away for the winter and in the spring because the oil will get acidic from condensation and sitting. I know some will say they have never had any problems but the price of oil is cheaper than an engine. Sorry for the rant.
