I too have to say I'm shocked at the mileage some folks are getting. My '03 4.7 Tundra got it's worst mileage ever during the breakin period with a crappy 15.5-16...Since then it's NEVER gotten worse than 18 and I was pretty annoyed at that, (it was towing a fairly lightly loaded trailor)...typical highway mileage is a solid 20-20.5 with the occasional dip to 19.5 or a jump of 21-21.5...it's done this for over 100K miles. Even when I've got 1500 lbs in the bed it holds 20+ on the highway. (and yes, I've done it more than once)
The Retrax bed cover may make a slight difference but I haven't seen a difference when I have it open vs closed. I'm using the smaller 245 tires rather than the 265-285's that a lot of the folks around here like so that may make a small difference.
No effort involved in getting the mileage either, I typicaly drive the speed limit or close to it 70-75, though I will sometimes pace the faster traffic at ummm somewhat higher speeds LOL...I keep the air filter changed at 30K miles, and use Mobil 1 (though I saw no difference when I changed from dino oil), I keep my pressures up at 35psi in the tires.
And yes I do know how to use a calculator.
