I towed an 8000 lb cargo trailer with a classic car to a Rally 3/4 of the way across the US, in mid-June with my 2022 TRX. 4300 miles in all at 70 MPH. I use an Andersen WDH. The TRX steers awesome, no sway, plenty of power, don't know the trailer is there. Got 7.1 MPG on the trip. I have towed similar trailers with a 1972 Ford 3/4 ton 4x4 High Boy, 390 engine, 4.10 gears running about 3000 RPM (great truck), a 1993 Ford F150 5.9L, a 2003 1500 Silverado 5.3L (gutless POS), many 2013-2020 Toyota Tundras 5.7L (awesome trucks). Every single truck got the same mileage. I have heard that the Ford's with the V6 get about the same assuming a comparable trailer.
I have towed the trailer empty at 4000 lbs and got the same mileage, so it is all wind resistance.