As title says check what your truck is getting for fuel.. along with size of engine and what kind of driving you do mainly and also what you get for towing... approx weight...
I have 07 4.0 tacoma and i get 16mpg, usually speed limit, mainly highway, and towing a 1900lb boat i get like 11mpg
I noticed its practically the same as the tundra
You've definitely got something going on there. Are you running oversize tires or something? Leaving the E-brake on? The suicide doors on an Access Cab open at 60?
I've got a 2010 4.0 4x4 Access Cab w/a slushbox, and I was averaging 22-23 with the original 245's, and since moving to 265 Duratracs I've still been getting 20-21 in mixed driving (50% back roads, 25% highway and 25% in town), and that's including the 11 stop lights I go through each way commuting to work.
What mods have you done to your truck that might be affecting your mileage? I've heard that the intake box power boost mod thingy gives you a power boost, but sucks your mileage way down. Same thing for some of the aftermarket exhaust systems. And of course any weight you add contributes to the problem, as well as any external add-ons and doodads that increase drag.