True that I'm no expert. Say if you are coasting down a hill and the coolant temp closes the thermostat, the coolant that is locked in the radiator is still cooling from the air flow. You will watch your temp gauge go down. Coolant transfers heat away best at 210. Now I don't know if this is with all liquids at a certain number below their boiling point or not. I do know that with automobiles 210 is thermal efficiency.