Possible stuck thermostat valve, I was setting at idle for about 10- 15 minutes and the dash gauge read low, once I drove about 3 blocks it went back to near 200. someone said that my thermostat valve was stuck. I have a 2007 1/2 2500. I noticed that it did it again but want to know is that normal or do I need to replace the valve? Thanks for your input.

 

Replace the thermostat. I would normally go with a 180 degree depending on where you are location and how cold it get outside during the year.