I am looking to add a short BB or leveling kit to my 07 Unlimited. It is bone stock with 4:10's. I am currently getting 18 MPG (BFG M/T 255/75 17's, auto), with combination driving. What is the average MPG loss as you move up in tire size, to 33's or 35's, with current gears? I don't mean to be lazy, I just hate wasting time (I don't have) searching for an answer.