WRONG! Once the thermo opens it mixes with the hot coolant in the engine to maintain the temperature. A 160 thermo will maintain 160 in the winter ambient air temps are to hot in the summer to maintain 160.
That is more or less what I said. Fact of the matter is that when its 85+ degrees outside, and you are running a 160 degree thermostat, it doesn't necessarily mean that your motor is running at 160. Its likely running much warmer because the thermstat remains constantly open. Same thing as not running a thermostat at all. The coolant in the radiator never gets cool enough to keep the motor temps down because the thermostat is always open.
