I know this has been beaten to death, but I 'll ask anyway. My truck temperature will rise to normal then drop back to the 1/4 mark. I think it's the thermostat...just wanted some more opinions. lmk

Also, on my last tank I went from 17.5 mpg to 15mpg. Might be coincidence.

 

It's the thermostat or temp sensor might be on it's way out.