If you're looking for a Jeep, with proper power level and gearing to perform decently off-road, to get more than about 15 mpg, you're going to be disappointed. These are boxy, non-aerodynamic vehicles tht aren't particularly light. Their forte is off-road use. From your description, you might be more satisfied with a small SUV with a 6-cylinder engine.

1977 CJ-7, fiberglass body, AMC 360 w/ headers, DUI ignition, Edelbrock intake and Holley 4150 carb, TF999, Dana 300, 4.56 gears lockers, York air comp, 4" susp lift, 2" body lift, BFG 35" M-T tires, Megashifter, AGR pump & box, REP8000 winch.