First long tow w/34 foot trailer

318 miles from Elk WA to Cove Or, rolling hills and then the grade into the Blue Mountains. This is all in the Eastern part of both states.
This the description of the grade. ( "Cabbage Hill" A 6-7% grade with killer curves. A very decieving stretch of road ) The ECO D handled all of it with class. I set the Transmission in 7th and we run in 6 or 7 at 59 to 61 MPH except I used 4th on the grade @ 40 MPH. The transmission got to 201 and 199 a couple times but all others were normal. I weighed the combination at the truck scale and it was 13,260 which was less than I thought it would be as the trunk was carrying a lot of items I move back and forth each spring & fall. We averaged 12.8 MPG hand calculated. The truck said 12.7. I was very pleased with that, the F150 I used before would have been in the single digits. On another note, about 30 miles of the trip was with out the tow/haul mode as we stopped at a big farmers market north of Pasco WA for our ice cream break and to stretch our legs and forgot to turn it on when we left. No wind to speak of till I headed east across the valley to the foot of the Eaglecap Wilderness Area where I live and it was out of the south and gusty so it was a tad slower going that direction.