2000 F250SDLB 4x, new Jasper 5.4 2v, AMSoil in every box, AFE intake, Magnaflow muffler.
10-11mpg city on winter blend fuel
14 hwy winter blend fuel
add 1-2 mpg in summer. DEQ up here adds to much crap to fuel.
I have just installed a new x pipe in front of cat that made a huge difference in performance now I am checking mileage.
I will look at Transmission slip and a programmer next.