Perhaps a drive in California is informative. Even motorcycles with a trailer have a 55mph posted speed limit, let alone RV trailers and semi trucks. My drive home from the AS dealership I did 55. I stayed in the right lane and was passed by every vehicle class. When I crossed into Arizona, I continued at the same speed, only I was passed by folks running much quicker than the posted 75mph. I was more interested in learning how the rig performed with the wind surges of the passing buses and trucks than setting a speed record. There are two lanes and one is called the passing lane. Unfortunately, the majority of drivers in the US lack lane discipline and even hog the fast lane at a slower speed.
I really do not care what TV one has, speed just magnifies any issues like a tire issue or avoidance of road debris. The faster one goes, the stopping distances are longer and quicker reflexes are necessary. I bought the AS as a device to enable relaxed seeing of the country side. I have done the faster driving in sports cars and on motorcycles and that faster speed required complete attention to the road, not the scenery. Ever come around a mountain curve and find a boulder in your lane? I have. Faster speed decreases one's options in a hurry.
The math from the gas embargo era was a 10% decrease in fuel economy per every 5 mph increment over 55. So running 65, one could use perhaps 20% more fuel than running 55.
WBCCI Life Member 5123, AIR 70341, 4CU, WD9EMC
TV - 2012 Dodge 2500 4x4 Cummins HO, automatic, Centramatics, Kelderman level ride airbag suspension, bed shell
2014 31' Classic model 30 twin beds, 50 amp service, 900 watt solar system, Centramatics, Dill TPMS, disc brakes, 16" tires & wheels