PowerStroke Horsepower and Torque
Hp and torque dyno numbers
I like to keep the engine between 1800-2200 as that is where peak torque is, peak torque=peak mileage in my experience
if you have 245/7516 tires 2000 rpm is 71.95 at that speed aerodynamics come into effect and hurt mileage due to the fact tires are rarely their mathematical size and differences in tire diameter from manufacturer to manufacturer your speed at 2000 would be closer to 67.22. Again anything over 65 and aerodynamics hurt your mileage so 1800 rpm would realistically= 60.49. That is great for mileage but a bit slow and boring, however 1900 rpm again adjusted for reality would be 63.85mph. A bit better as far as boredom goes but still on the edge of ok for mpg.
All numbers were figured with the following formula
(Rpm x tire size)divided by (gear ratio x trans ratio x 336) = mph
I get bored and do this math while driving