We recently pulled our trailer from Florida to Grand Teton/Yellowstone and return, covering a total of 5211 miles in 3 weeks. Of that number, 4785 (88.43%) was actual towing and the balance was without the trailer. Just want to throw out some information for those that might be planning a similar adventure.
Our towing/trailer setup: 2020 Ford F150 Lariat, 3.5 EB, 3.55 e-locker, max tow package, bone stock. The trailer is a 2021 Jayco Feather Micro 166FBS which weighs 4095 lbs. unloaded and has a 4995 GVWR. We are probably right around 4800 lbs. loaded. The vehicles are connected by an E2 weight distribution hitch.
We normally carry 5 gallons, or less, of fresh water with gray & black tanks empty when travelling. We tried to maintain a speed of 65 mph for consistency and more fuel economy. We actually get better fuel mpg at 62 but felt that speed would be too slow on interstate highways. The best efficiency for us is achieved by pulling the trailer using Tow/Haul mode, and locking out gears 8, 9, & 10. In some areas of high wind, I tried reducing the amount the turbos were running by shifting into 6th gear and raising the RPMs. We found the gas mileage actually went down so I kept it in 7th gear.
Overall miles per gallon for the entire trip were 12.58 according to LOM, 11.66 calculated manually. The MPG for only towing was a range of 8.91 14.17 (calculated) depending on environmental influences like wind and hills. The overall combined MPG range was 8.91 - 28.10. Yes, that is correct 28.10 MPG was achieved during a 191-mile trip around the Grand Loop in Yellowstone which has a 45-mph limit. The LOM reported 29.2 MPG but was adjusted to 28.10 by manual calculation. (I took a picture of it because I could not believe it.)
Some other observations:
We used 483.542 gallons of fuel in total for the trip.
Lowest fuel cost was $2.949/gallon in Arkansas.
Highest fuel cost was $4.819/gallon at Flagg Ranch, Teton National Park.
Head winds would reduce MPG by 25% quite easily.
Conversely, tailwinds are awesome!
Based on forum posts put forth by others, I was quite concerned of engine and transmission heat issues when we hit the steeper hills and inclines. We had no issues with overheating in engine or transmission during mountain travel. In fact, the gauges did not move at all from normal operating temps, and ambient temps were mid 80s to upper 90s.
I know some folks do not care for the assist provided by engine braking, but I found it helpful.
Best roads - Alabama with the exception of Birmingham and Montgomery metro areas.
Worst roads - Denver, Oklahoma and Memphis.
I-40 between Little Rock, AR and Memphis, TN has a large population of semi-trucks. My uninformed estimate was around 80% of the vehicles were trucks.
Our longest day of travel was 608 miles, which speaks to the comfort level of the tow vehicle.
Some people are simply inattentive drivers - see example
Our trip was unfortunately cut short due to a mechanical issue that requires attention. While driving the Grand Loop, a low, growl/whine was detected in the driveline. It was speed related, but not due to tires since the tone of the noise did not change when we went over different types of pavements.
Prudence dictated that we get it checked out by a mechanic and they verified that the noise was coming from the pinion bearings. They said it was drivable, but we should get it repaired ASAP. (Their earliest opening was October 20!)
Overall, we were happy with the results of the trip, and of course, the views and wildlife are awesome, even when having issues. Like I mentioned earlier, just throwing this information out there in case someone is wondering what a trip such as this might look like.