I had a 13 F150 with 5.0, 3:55 gears, 255/80/17 tires, 5.5 bed, lifted Bilsteins and it got 18.5 mpg.
I now have a 14 F350 with 6.2, 4:30 gears, 315/70/17 tires, 6.75 bed, lifted Bilsteins and I’m getting 13 mpg. Both rigs have/had toppers and were/are driven similarly-not aggressive but not...