That's true, it'll pass anything but a gas station! Those mileage numbers are pretty accurate too, although "goodcruisin" makes a good point in his post as well. I don't make frequent fuel stops with my 39 gal tank in the burb, but it sure empties my wallet when I do!
At any rate, the OP hasn't shared any info about why he's buying a new truck other than to increase payload, so we don't know what size rig he's towing, or what he's towing it with now. The DMax he has scoped out is certainly not a bad choice if it's in good shape.