I have a 2016 ram eco diesel 4x4 crew cab with 3.55 snug top camper shell. Just took it on its first two road trips the first one from NM to KS got 27.1 on the way there and 21.2 on the way back fighting heavy wind from a storm. The second trip from NM to Co got 26 mpg round trip. Now I don't drive the way one should for max mpg I go five over the speed limit all the time and take off fast from ever stop. I'm pleased with the mileage so far, the truck just has 9,000 mile.