the oil doing what it is supposed to d0, carrying the heat from the combustion chamber
I don't know where this every got started, but oil does very little of the cooling on a model engine. The specific heat of oil is quite low, and the volume is only about 1/6th of the fuel. Much of the "cooling" is the expansion of combustion gases which extracts the power from the fuel. Most is from the air passing over the head.