That sounds a little low (that's just my opinion). I personally get 16 city and 20+ highway and I really don't drive for the best fuel economy either. From what I've read about most others on here is that the averages for the 4x4 group is 12-14 city and 16-19 highway (that's just what I've read). The two wheel drive group seem to do a little better. Of course around here most people have added larger tires, lifts, and extra weight in the form of offroad armor, and mpgs really start to drop with those kinds of things. Also, be sure to actually calculate your mileage a couple times and don't just go by what the computer is telling you as it has been known to not be 100% accurate.
... oh yeah, almost forgot, before someone else says it: it's a truck, it won't get good gas mileage. :laugh: