We are beginning to look at travel trailers. One consideration is the cost of towing the unit. With the Middle East situation and with the government saying that our highways are seriously underfund...
I agree with everyone else that frontal area (size) and wind resistance (speed) are the biggest mpg killers in the flats, but in the mountains your combined weight comes into play. In the flats I keep the speed down to no more than 60 mph, but I try to get a little momentum when approaching a hill by speeding up a bit.