Fuel Gage

[miki_373]

Hi guys. Im new here and new to 6.0 powerstrokes. Ive just got my truck and there are some weird things happening with my fuel gage. The gage seems to show different level with every engine start. Its usually showing less fuel in the tank but once it showed full tank when in fact there was no more then 3/4 of a tank. I haven't had a chance to check the actual mileage of my vehicle since I'm still on my first tank, but with the gage position I'm able to guesstimate 7 mpg. Is it possible the gage is screwed up or could the mileage be actually be that bad.

Truck's got stock rims & tires, cai, streight pipe, 4x4. Also, there is 40k miles on the truck.

Any help with be most appreciated. Thank you all.