I have a 2000 with 3" of lift and 31" tires and get about 15.8 doing 70-75. Not sure of the in town milage. Before my lift with stock tires I was around19-20 on the highway. I used to get about 300-320 miles on a (looking at fuel guage) tank before I needed a refill, now I'm down near empty at 220-230 miles. My fuel guage doesn't always seem to be accurate because the needle will be down over the E and when I fill up it only takes 13-14 gallons. Other times when I fill up it won't show completely full even though I personally topped it off. It's a bugger to remember to turn on a gps device in the vehicle for every trip for a whole tank of gas but it will give you better numbers to work with. I still have more tune up stuff to do to my jeep and will post with any real gain in milage based off of gps and actual fuel consumption at the pump. I'm guessing here but since this was a pre existing problem before the lift it is most likely a sensor or other engine management issue. O2 sensor issues would be my thought. Also clean your engine compartment grounds(battery ground and engine ground. Make sure the electrical system has good gozintas and gozoutas for the electrons flowing throughout! start with basics first then progress to the hard stuff. My jeep would show no buss on the odometer and my rear hatch light would stay on with the engine off, after I cleaned up the grounds haven't had that issue since.

 

Agree with you 100%. I already have all the after market mods and I am still doing 10-11 gpm. Starting to remove them one by one, until I figure out what is going on...

Brakes have jut been done new - so no dragging there... CAT replacement is next...

 

Wow! 10-11 gallons per mile? That's real bad! Haha