Duke
I have a couple of friends in our church camping group that have the same truck as mine, pulling similar weights, going to the same locations at the same time, and the mileage varies from 9 to 13 mpg. We're at about 16K plus about 8K for the truck, so you're a good bit lighter. The point is that there are so many variables in tires, tire inflation, speed, headwind/tailwind, steady foot or not, cruise control or not, and driving habits in general that it is almost impossible to determine what a particular driver will see in mpg in a particular truck towing a particular trailer. I believe that all these factors affect mileage to a much greater extent when towing than when driving in general. I can tell you that the mpg drops very quickly when you exceed 2000 rpm's, which puts you at the low to mid 60's mph. I would not go by the truck DIC for mileage numbers, hand calculate full tank to full tank only over substantial distances.