The last 4 to 5 weeks i have noticed that my truck is only averaging about 13.5 mpg. This is on the calc, i don't have a lie o meter. I was averaging around 15.7 before. Nothing has changed in this time period. Same driving habbits, same trip to work and back, same outside air temp, etc. The only 2 things that were different was that i took off my tonneau cover to go pickup my camper and i also switched to the white winter bottle of power service, instead of the grey summer bottle. Those are the only 2 differences. Could the power service change my mileage that much from the 2 different bottles? Fuel filter was just changed 2k ago. Oil is in good shape, not rising like i'm getting fuel in the oil. No extra smoke, truck runs fine just like always. Coolant was a little high, but thats because i added a bottle of additive and never drained any coolant to make it equal. Any ideas guys?