Its important to remember that XJs are about as aerodynamic as a brick. Whats more, the I6 has to work a lot harder for those of us with bigger tires, which also has an effect on MPG. Lift kits dont help either. Roof racks also create a lot of drag as well. I know I'm stating the obvious here, but I think sometimes we forget. You can only squeeze so much out of these Cherokees. My 98 on 31s and 3.5" kit gets about 12 combined MPG.

I get ~19 averaged with mostly highway driving, and I'm about to up to 31s from 225s. Hopefully I can keep it pretty high. Maintenance is key!

Just did a 200 mile trip with a 98 classic. Towed an empty trailer there and on the way back had a total weight of 2000 pounds behind it. Got 15 mpg mostly highway. Funny thing is that's only 2 or 3 less MPG's than unloaded. These things are tractors.

My 2000 XJ is mainly stock (no lift yet). It hasn't had a real tune-up yet but I have been working on it and am about to remedy that. The tires are Goodyear Wrangler, slightly larger than stock size.

Anyway, my average city rush-hour with AC running mpg is around 13 mpg.

I just did about 5 hours of highway driving at 70 mph; I got around 16 mpg with the AC running, and around 17 mpg on the return trip with no AC, and windows down. I would imagine that doing it with no AC and windows UP, would improve on that.

Do you still have stock gears? I am planing on running 33's with 4.56 to even it out

Yup, still 3.55s. I would like 4.10s, but money is tight at the moment and I don't really know how to swap the gears myself.