Do a few more trips and your truck will be broken in and you can see if it improves. You never know, you could have a 10 mph headwind that will screw up your mileage on a trip and you wonder why 60-65 mph was getting low mpg. That would act like driving 70-75 mph and that will start killing your mpg's.
I have a Cessna air speed indicator in a center console and pitot tube sticking out of the grill. I can see when I'm "in the draft" behind a semi or coming back from mexico and hitting a 25 mph headwind. No wind with the diesel setup towing in my sig is about 14mpg at 65, with a 25 mph headwind it's like 8mpg, with a draft or tailwind sometimes 18 mpg.