if it's a automatic, you can take off 5 to 10 MPG...especally with oversize tires(reguardless of gearing).
My commuter is an auto and I'm getting 27mpg +/- 1mpg every tank. Wait... is this helping? 
-Eric
that sounds about right for a stock one... yours is 2 door right? 2wd or 4wd?
the one i just bought for my wife(stock 4door auto) is getting 23 MPG, but has the original O2 sensor(ill be changing it anyday), but her old one (stock 4door 5 speed) has seen 33 MPG HWY and gets a regular 26-28 in town........keep in mind....
SHE HAS A VERY GENTLE RIGHT FOOT! 
.............i drive it and it gets 22MPG
