Review on the new 7.3 Ford V*

ron.dittmer wrote:

mleekamp wrote:
I'd say it's more about the wind resistance than the weight of your RV that affects mileage....

I agree that the aerodynamics of the rig will influence the fuel economy. I am no expert, but I feel it could be nearly as influential as the over-all weight.

Aerodynamics have a much greater effect on fuel mileage than weight for highway driving. On level ground and at a steady speed, the only effect weight has is to (slightly) increase the rolling resistance of the tires. Air resistance, on the other hand, make up the greatest part of the friction that must be overcome, and further it goes up tremendously with speed increases--it's proportional to somewhere around the cube of the vehicle speed, if memory serves.

For climbing hills, and for stop and go driving, the weight is relatively more of a factor than for highway cruising.

The aerodynamics of the rear of the vehicle are at least as important as those of the front. RVs generally are pretty terrible at both ends; a squared off back generates lots of turbulence and drag, which is why airplanes and Priuses tend to have pretty pointy backs.