Operating temperature

The primary purpose of the thermostat is to get the engine to normal operating range as quickly as possible. This reduces wear, improves efficiency, and reduces pollutants. The latter was a primary driving force in increasing engien operating temperaturesd. As an aside, it also gets the water hot for the heater/defroster. I don';t know what the boiling point the new delco coolants are, I suspect at least as high as ethelyne glycol/water mix. A 50/50 mix has a boiling point around

225-230 F at sea level. Each pound of pressure on the system adds about 1 degree F to the boiling point so the boiling point of a system with a 15 lb cap at sea level running half ethelyne glycol at sea level is in the neighborhood of 245 to 250 degrees. The transfer of heat from the coolant to the air in the radiator increases with increased temperature differential so the radiator size can also be reduced.