Rear-End Gear Ratios

[Hammerhead]

Hell, I get 7 USmpg with my big-rad non-aero truck with my wind grabbing parachute of an equipment trailer empty w/ a jeep & booster stacked up weighing 70k. That's at 55-60 with 4.10 rears w/11R22.5 not low rolling resistance drive tires pushing those great big definitely not lrr 385 wide steering tires.
If you pull a box trailer, especially if you've got the side skirting and stuff you should be kicking my @$$ all over the place in the fuel mileage game.
The "old myth" that countless truckers spew about "I get better mileage at 70 than I do at 60" is such BS I don't even laugh at it any more. Physics doesn't change, that's why they call them "Laws of Physics". A physics fact, as speed increases linearly, aerodynamic drag increases equally, however as aerodynamic drag increases linearly, the power required to overcome the aerodynamic drag SQUARES!!!