Bob, I agree about all of the variables that contribute to good mpg. I know properly inflated tires also plays a role. However, my calculations without the tow vehicle was a 500 plus mile trip to central Fla. I tried everything including coasting at every opportunity.
I would like to drive by using a fairly constant RPM but I would get run over by the semi trucks. My transmission downshifts at every opportunity, except at around 45mph. Little grade, one gear downshift. Little bigger grade a two gear downshift, and that's with cruise on.
Now that diesel is the same price as gasoline, I'm thinking I may have sold my Diesel Pusher a little too cheaply.