I was having concerns because my temperature guage was reading very cold at times and very hot at other times. I discovered that my thermostat was stuck in the open position using the Mr Gasket thermometer radiator cap and that my temperature guage was working normally. After replacing my thermostat, my Mr. Gasket thermocap read 180 degrees exactly; which is where the new thermostat is supposed to operate at and 180 degrees is the recommended operating temperature for my vehicle. The Mr. Gasket thermo-cap is a good diagnostic tool.I found it difficult to get the Mr. Gasket radiator cap on. I thought at first maybe I received an incorrect part. I had to use significant pressure and twisting force to get the radiator cap on. It would be exceedingly difficult for my Mom, girlfriend or some one not as strong as me to get the radiator cap on and twisted close. "This" is why I didn't give a 5 star rating. I would give a 4 1/2 star rating or an A, almost an A+...