Hi All! Pretty serious about changing from Class C motorhome to Truck-trailer combo, due to overall costs associated with driving it. The biggest trailer we're looking at is about 8,000 dry & 10,400...
There is no free lunch. It requires X Joules of energy to move a mass at a certain velocity. Doesn't matter if it's a 14,000lb Class C motorhome, or a 7,000lb trailer and a 7000lb truck.
Some efficiency can be gained through time and technology, but not significant enough gains that will pay for themselves. You can buy a LOT of gas for that paid-off Class C before you even come close to a payment on a new truck and trailer, even considering trade-ins.