The 6.7 is a 2018 F350 double cab dually and averages 14 mpg. The 6.2 is an 2019 extended cab single wheel F350 with a Deweze bed, Deweze feeder, and ranch hand bumper. It gets 9 mpg with street grips and everyday driving. Drops down to 6.5 mpg when towing. In the summer if I take the feeder off it'll get 9.5 mpg but I've never seen it say 10 mpg. I did have all terrains and it dropped to 8.5 mpg.That seems poor mileage for the 6.2. I've never run a diesel so don't know about that. My 6.0 GM products and my Hemi always got at least 16 or more until I towed with them. The hemi was the worst, any trailer at all would decrease the mileage to 7.