Just curious......

Never had a diesel truck, but over time, I came to this conclusion re tow vehicles and towing. All you can do is make sure your truck is running properly and up to specs. After that, any checking of gas mileage is only good for monitoring any change that could be indicative of a problem. Otherwise, ignore the mileage as it's never that good when you are pulling a trailer with flat surface areas that create so much drag and resistance. There are no "miracle cures". The only thing you can do is keep your speed down, manage gear shifts where applicable, accelerate gently when possible and keep the truck in top condition. Aside from that, fill the tank when necessary and just enjoy the ride!