[Big Dave]

My truck is the poster child for gearing-derived MPG.

With my (now unavailable) 3.08 gears, GV overdrive, and manual overdrive, I limit my RPM to 1325 @ 70MPH.

Result: A 8,000 lb truck that gets 24 MPG with an open bed (my tonneau blew off on a strong side wind) in mixed driving, all done at the posted limit. Low RPM saves energy by minimizing engine frictional HP. Like aero drag, EF HP goes up with the cube of RPM. You really don't want to rev a 444 over 2,000 RPM under any circumstance.