It is true that 50 to 55 mph does give your mileage a significant boost. For free.
However, when I tell non-RV people that 250 to 300 mile per day is a good average, they have a hard time believing that. Then if I add driving at 55 to 60 mph to increase gas mileage they just shake their heads.
To drift a bit off topic, I think it is safe to say from the response so far that the average RVer,
• Does not worry about a mile or two more per gallon. It is a small portion of the total cost.
• Is not a Marathon driver, expecting about 250 to 300 mile per day. I have pushed harder to reach a known destination and set up.
• Will drive 65 mph or less. I will admit I have seen a many exceptions.
I could be all wrong here and just looking at it from an old man’s perspective.