Recently we sold two vehicles and traded a 4Runner in on a 2018 2500 Duramax ext cab 4WD. We had three vehicles were used for different things so between heavy tractor and trailers to the lightweight camper this fills all our needs and we are very happy with it. In reality it is the quietest vehicle we ever owned.
We were towing the camper at 65MPH. The DIC displayed an average of 17 MPG on the way there. I can say that the winds we drove through were some of the worst I've ever seen almost pulled over and stopped more than once. On return trip again at 65 MPH we made an average of 19.8 according to the DIC. We had about 2000 miles when we started so I know that when manually checking the MPG the DIC is within +/- .5 what I figure.
Just driving 70MPH empty we are averaging 23 to 24.
We love our new truck!