We had the Monte out to a local State Park last week for our shake down trip and noticed a nearby camper with a deflector on his Dodge. I asked him if he got any increased fuel economy and he replied that he didn't check his mileage (which I took to mean, he didn't get any additional fuel economy) but he did say that the bugs didn't mess up his trailer front like they used too. That's an expensive bug shield.
I think I'll jsut save the money I would have spent on a deflector. I can always clean off the bug splatter.
It has been pretty well documented that they do not work on a truck/RV combo other than a expensive bug deflector. Look at how the defelectors are configured on a 18 wheeler and that will give you a idea of why they do not work on a PU/5th wheel. The turbulance is in the PU bed a deflector on the roof will not do anything for that.
I had one on my 95 dually gasser. It was a good bug deflector for the front cap ... it made an awesome water swirl in front of the cap while driving down the road during a rain shower ... it put a dent in my wallet ... it did nothing for my fuel milage. Sold it at a loss.