I pull a 9000# fifth wheel, and on a trip from Tuscon to central Washington averaged 10 mpg wit a 2019 Limited, e-torque at 55-60. Played around with the speed a little on the flats, and found the sweet spot. Truck loves 55 mph when towing, and never had a problem. As speed increases, mpg falls off radically. Keep the speed down and be safe. Let the fools pass you. At 60 mph you are getting 1 mile-1 min. At 75 you are getting 1.25 mi per 1 min. So, a 3 hr trip gains 30 miles for the 3 hr for roughly a 10% gain in time, but a nearly 20% loss in economy. I guess it depends on how much your time is worth, and if the danger to yourself, family, and other drivers is worth.