[Trevor]

Originally Posted by Huskymaniac

Thanks guys. I had the thermostat and radiator cap replaced today and the radiator flushed. There WAS a thermostat already installed so it looks like the previous owner and the dealer who sold the car did NOT try to hide the problem by removing the thermostat. On the 25 minute ride home (about 78F outside temp) the temperature gauge seemed to be more stable but it was still not dead still. It was also still below the horizontal level. I guess there is still the chance of a head gasket issue but the fact that it runs cooler than normal is still a mystery to me. Why would a leaky head gasket cause an engine to run cooler than normal? I doubt there is an issue with the water pump for the same reason. That would make the engine run hotter than normal, not cooler. The only other possibility is the sensor or what people call the sender unit. But the temp reading isn't erratic. It moves slightly but logically. I suppose I should find a big hill and give it a test. The mechanic said the coolant was clean so that is a good sign.

I think you have been logical all through this issue and have now written your own answer. Automotive gauges are produced at a price and are not designed to provide exact calibrated accuracy.