In this weeks RV new letter, I saw an ad for AirTab. These plastic pieces are glued to the rear of the RV for better air flow and performance, which I am translating to better gas mileage. Do they...
I've been using AirTabs since about 2006 and they do work to increase stability.
As others have said, the effect on fuel mileage is small enough as to be undiscernible to me. However, they are worth the additional stability on the road.
These type devices work on airplanes to provide lift benefits on the wings. The principle is the same to provide stabilizing benefits on our rigs.