I have 35’s on mine and a leveling kit up front and add a leaf in the back. 3.55 gears. I don’t see much difference on the lie-o-meter toggling between 5th and 6th gear on the interstate at 70+. Really wish I had 3.73 or 4.10. But not enough to change. I really think I would get better mileage with 3.73, but I could be wrong. Regardless the higher you go the worse you will do on fuel. Can’t say how much. What I did cost me about 2 mpg. 37’s and more lift will be 1-2 more if I were to guess. I was getting 16-17 on my daily commute, before I lifted and did tires and wheels. 14.8 was my 7,000 mile average after lifting and doing 35’s. Now I have ******d and I’m at about 18 mpg average since the ******, lifted 2 on 35’s. Hope this helps