[nUcLeArEnVoY]

Originally Posted by P@blo

If a thermostat is rated to start opening at 180*, are we suggesting that the cooling maintain that temperature even when the valve is not fully open? I'll put my helmet on for this one as this makes no sense. It seems nornal to have the operating temperatures 15-20* above the thermostat rated opening point.

Some guys have probably over engineered their cooling system and can maintain coolant temperatures when the thermostat valve is only partially open and is what I think is actually going on here. And maybe to a lessor degree, guys with more modest cooling systems but with cooler air temperatures (less demand on system) see the same situation occuring. Seems to be a bit of stretch to say a cooling system has "lost control" not maintaining the thermostat rated starting opening temperature but never overheats the engine. My cars run 180* thermostats and typically run 195-200* no matter what I throw at them, driving style wise, and see almost zero ROI chasing something like this down.

Yeah, this is what I was always led to believe. A thermostat's purpose is to maintain cooling system pressure, and to set the minimum operating temperature. The cooling system's capability and efficiency is ultimately what determines the temperature the car runs at. If your cooling system is bulky and well-designed enough to actually open and close a 160 thermostat in closed loop operation, then great, If not, it'll operate at a higher temp and eventually stop at what the cooling system can support. The only issue with using a thermostat at too low of a temp that your cooling system can't maintain, is that said thermostat will always be open and you lose some of the system's ability to make pressure.