aerodynamics

The Airstreams, Avions, etc. do make a big difference in the way they tow. It isn't all measured by mpg, but by the way they handle. The low center of gravity and decent aerodynamics make them stable, even at higher speeds. They don't sway as much in cross winds and tend not to be affected as much by passing semi trucks. I have towed plenty of trailers and the rounded aluminum trailers seem to tow the best and the higher the speeds, the more noticeable to difference is.