He drives a lot, regular non-stop trips to Vegas for example, a solid 12 hour trip each way from here. Besides, he claims he gets the same mileage whether he fills them or not.
I was spending so much for fuel with my old truck that for a while I tried only filling it halfway each time hoping that the lessened weight would help the fuel mileage, but for some reason it made it worse. Not just a little, but a whole MPG - that's a lot when you only get 16 to begin with.