We have a 3.7 auto tranny. I seem to get 17.8 for mixed highway/in town. About 22 on the highway at 60mph. The Jeep has 135K on the odometer and I have big tires and an OME lift. Check my signature line. I carry a lot of recovery gear and tools in the back including a couple of 15 foot chains. Not great gas mileage, but I love my Jeep. We tow it behind our motorhome and use it for fun offroad on our trips. I also have a 2003 Honda CRV with 165K miles that gets 27mpg on the highway and 22 around town. Guess which one gets towed on trips more often? Did I mention that I love my Jeep?

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Jim

2003 Liberty Renegade
Leather Electric Seats
Self-Dimming Mirrors
Sun Roof
MOPAR Rock Rails, Skids, Rear Hitch
EMU Heavy Duty shocks and Springs 2.5" lift
Front Tow Bar (for RV)
Firestone 255 70 16 Destination AT Tires
Straps and Chains

I have a 2003 Renegade 5 speed. I get about 16-17 around town and about 18-19 on the highway. But I also have a 2in lift, spacers, wider tires and light bar. Everyone is always shocked when I tell them my mpg, they always say thats too low but its a very reliable vehicle and its fun

I personally have an unmodded KJ in terms of things that would drastically effect my mileage, I shift very conservatively and try to drive for optimal fuel mileage, 50% to 60% highway at least. I average 19.3 to 20.5 every tank. My lowest is around 18 flat and happens very rarely. My max is 21.7 on a road trip using 70-90% highway, however, my mileage average is around 20.0 MPG through at least 30 tanks of gas. Overall, due to my consistent and conservative driving style I have managed to report numbers consistently higher than the EPA estimates and am on the run to save $650 in gas per year in comparison to the EPA estimated annual fuel cost. Overall I find it easy to return such numbers on my Jeep which as I mentioned is unmodded and has fairly low mileage (50k). However, you should note that extended highway driving does not really increase mileage which is not optimal. On top of that, if you lose your patience you will see larger drops than anything you will ever gain back by trying to save gas.

All of this is simply based on my experience with my Jeep and I hope I helped influence your choice for the better.