After I got 285/75/16 tires the Trooper did 13.5 MPG. Last week I put back my stock size tires, and looks like it make 12 MPG. May be this happened because I have to push it for higher RPM for get same speed.
On 285 the Trooper eats one tank for trip from LA to Las Vegas.
By the way, I never have MPG, which displayed on sticker.

2001 Trooper LS 3" lift,no more Rancho 9000RX,
no more 4L30E transmission,
ProComp 8" 130W driving lights,
Surco roof rack (modified),
110V power outlet, Viair 380C compressor,
CB/FRS/GPRS/HF/VHF/UHF Radio, 285/75/16 BFG AT/KO.