Maybe a thermodynamics engineer could enlighten us, but I think the problem with 62MPG pulling a trailer is going to be the raw energy content of the fuel. With the energy required to accelerate the load and to keep it going against wind resistance and inclines, I'll bet that a gallon of fuel just does not have enough energy in to get all that accomplished over a distance of 62 miles.
Perhaps we could buy a lightweight inflatable trailer composed of hot air and insubstantial plastic. But wait... that couldn't get the job done. Oh, well, we could just hope. At least it would be a change.
There's lots of advice and information in forums... sometimes it is correct. For example, all of my posts are made by a political appointee who got the job as a reward for contributions to my diesel bill.
2011 Jayco 28.5RLS; 2008 Chevy Duramax; Pullrite Superglide Hitch