[red82gt]

Hook up a temperature guage with numbers and tell me how often it reads less than 192*, thats how often the thermostat will be closed. Then throw you theory out. An efficient engine should run at above 200*F at all times which means that once operating temperature has been reached it will be open. The thermostat's job is to keep the temperature high enough, without a thermostat at all, the motor runs too cold and stays in open loop mode, causing it to run inefficiently. Also, the radiator will pull more heat out of the coolant when the coolant is being circulated, not when it's stagnant. Notice how if a car is shut off when the temperature is way up the coolant will start to boil just after you shut it down, not before?
Saying that the thermostat keeps the coolant in the radiator to cool it is pretty darn backward.