Cort, I think a good part of this is driving for mileage and keeping the speed down. Our old camper fits nice and low to the truck so there's a little less wind resistance there. One time, due to weather here, we needed to make up time heading down 95 to Beaty, NV. We drove 70 mph into a strong headwind and barely got 14 mpg that tank.
Ski, you and I have a very similar setup, except that I have a manual tranny. Our mileage is also very similar. Driving the low speed highways in the Sacramento mountains, I typically get 18 or 19 mpg, sometimes as high as 20 mpg. On trips that include dirt roads, it can vary more, but, like you, 18 mpg seems to be average unless it's all 4x4. I also agree with you all that air resistance is the real killer, be it headwinds or high speed. In those cases 14 - 16 mpg is expected. Until there is a small diesel truck available in the US, I will keep my Ranger, I think.
