[FrankieD]

Well Said

Originally Posted by MagmaJct

Your cooling system, radiator, fan, etc... set the maximum engine temperature. The thermostat sets the minimum temperature. Running at the proper temperature does many things, most have already been stated. One not mentioned yet is improved thermal efficiency.

When a fuel is burned it produces heat. The heating of the gases in the combustion chamber causes an expansion of the gases which produces power by exerting force upon the pistons. The cooling system removes some of this heat. Removing the heat also reduces the rate of expansion of the gas.

Earlier engines were not designed with emissions and economy in mind. They ran with cooler thermostats. With the engines running cooler gasoline vapors would condense on engine surfaces and fail to burn, and not contribute to power. But installing hotter thermostats, the internal surfaces are able to run hotter and greatly reduce gasoline condensation on engine surfaces.

This improved thermal efficiency of the engine, and allowed fuel systems to be tuned leaner since less fuel was condensing inside the engine. This also had the effect of reducing emissions, reduced the amount of gasoline finding its way into the oil. Engine wear was reduced over the model years, and modern automobiles today have much longer oil change intervals as a result.

My advice? In stock applications, use the correct thermostat for the engine installed. This should not matter what the climate is. The thermostat sets the minimum operating temperature, not the maximum. 190F is going to be the same whether it's in Arizona or Maine. The only difference is that in Arizona the thermostat will be open more than the same setup in Maine.

Most automotive textbooks cover this topic very well.