Without paying much attention to driving differently (I drive easy most of the time, though), I get consistent 17.5 mpg figures around town with 32" tires, auto, 4x4, Shrock bumper and skids, lights on the bumper and roof and running 32 psi in the tires.

Granted, "around town" for me is somewhat rural, with most roads having speed limits from 35 to 55. Still, I do drive a very short commute (1.8 miles each way) to work. Short trips such as that tend to drop your mileage a bit.