I just recently purchased a 2021 3500 High Country Duramax and have 7000 miles on the engine. I moved up 13 model years from a 2008 2500 Silverado LTZ Duramax I lightened my towing of a 5th Wheel with a weight of 16,000lbs to a Northern Lite Truck camper weighing 3500 lbs I feel my fuel economy is horrible at 11.5 mpg I was getting that mileage pulling 16,000 lbs with my 2008. I’m getting no help from the Chevy dealership after spending $75,000 for the new vehicle. The design of the Truck Camper is 2 1/2 ft lower than the 5th wheel and has a better aerodynamic design than the 5th wheel Has anyone else experienced this poor fuel economy with 2020 or 2021 6.6 Durmax diesels