[webnrrd2k]

I don't see how water jackets, pistons rings, and their tolerances are directly relevant here. The topic was bearings, and their lubrication and wear, in the larger context of warming up your car before driving in cold weather.

[sokoloff]

Imagine a cold-soaked engine with an aluminum piston, steel rings, a cast iron sleeve in an aluminum head. The aluminum piston will heat very quickly compared to the cast iron sleeve in an air-cooled engine. (There’s a massive aluminum heat sink in the form of the cylinder head.)

For a water cooled engine, there is a water passage around 3/16” from the cylinder wall which helps to bring the cylinder up to an even temperature more quickly and prevents a high heat flux from expanding the piston to the point where it can scuff the walls.

It’s not only oil pressure that is a concern for a cold-start to operating temps.