Welcome to the forum. If you do a search here you will find many threads about Tundra fuel mileage. There is quite a range of mileage figures reported. My 05 Tundra AC 4x4 is not great on gas either. Some people claim better mileage that the actual EPA rating but I personaly find this hard to believe because my 05 has NEVER matched it's EPA rating no matter how easy I drive it.. My 05 does no better than about 11 MPG city and 15 or 16 highway, less in winter. About all you can do is just check for the obvious things like sticking brakes and possibly take the truck in to get checked over in case there is a possible problem. Other than that just keeping the tires aired up properly and air filter changed often and using synthetic oil there is not much else you can do. It seems that some trucks of identical year and model will just get better or worse mileage for whatever reason. Yeah I know it sucks, I love my Tundra but am not thrilled with the mileage either.