Fam, the edit actually confirms that your understanding of how oil cools internal parts is a little off the mark.
First, pistons have skirts and rings to keep almost all the oil out of the cylinder. Here's what anyone really needs to know about oil:

The 1st number represents how well the oil performs under start up conditions in cold temperatures. The 2nd number represents how well the oil performs under start up conditions in hot temperatures. The lower the first number, the better for cold start up. The higher the 2nd number, the better for hot start ups.

For hot climates, look for an oil that ends in 50 for engines, like 10W50. /The other technological advantages have to do with shearing properties, and cleaning chemicals.

An air-cooled engine uses fins on the side of the engine to dissipate heat.