Sorry for the long winded answer, however, that would seem to be a hard question when you take into consideration of what engine mods if any were done, of where people are living, when and how they are driving the car, how accurate the gauge, what type of cooling system they are using ( radiators, fan, fan blade, electric fan, 1 or 2, additives ) thermostat rating, etc.. I think I would ask what is the best temperature the engine should run at. Find what mine was running at, and verify the gauge is basically correct. Then work towards my goal. I probably just didn't understand you question