I experimented my two camping trips trying to keep my speed down to 65mph on the interstates for mileage. I did not keep as accurate a log as possible & just went off the truck computed MPG. I used the cruise control set at 65 as much as possible on the first trip, 500 miles total. Second trip, about 250 miles, I just kept up with traffic about 70mph, sometimes hitting 75mph.
The truck calculations said I got better mpg in normal transmission mode over tow/haul mode when towing. On my first, slower trip, I locked out all overdrives (8,9,10), using tow/haul every time I thought of it (reverts to normal on startup). On the second, I mostly just kept 9 & 10 locked out. That one level of overdrive, in flatter road sections, seemed to make the difference, even though at higher speeds. I intentionally left normal mode on after initially forgetting to select tow/haul.
Yes, wind is a variable factor in mpg. BUT it is out of your control, last I knew ;)
