Update.......... Replaced the thermostat Friday night. The o-ring gasket was starting to go bad. The ASE tech I talked with told me that when the trans went bad, it overworked the thermostat. When this happens at his dealership, The thermostat is replaced. Added 1bottle of Amsoil Coolant Booster, and refilled the system. Ran it up to the Williamsgrove Open the next day. Temps never got above 200 on the hills. Ran 344 miles, and when I filled up, my fuel mileage was 21.1 mpg. This coming Saturday, we are going back to PA to bring home a 32ft. travel trailer.