OK friends. I've read fuel mileage for a 35' gasser with the v-10 Ford engine pulling a 3500 lbs toad will be anywhere from 4 to 9 mpg. This is average traveling, not all level and not all hills. ...
Some states do have speed limits. Many if rig is over 10,000 or towing are required to follow truck speed limits. Speed limits are the maximum speed not a requirement.