wind "adjustment" devices have frequently been discussed here. be it air tabs, those deflectors that mount on the roof of the TV, etc.
In the American Profile May 12-18 issue there was an article "Incredible Kid, inspired inventor, about a teen who streamlines boxy school buses with a $30/8 lb. shield which supposedly increases gas mileage by up to 20 %. Of course it also increases mileage by up to 80%/90%, etc. depending on how much fluff you want to use.
when I bought my Uhaul type trailer they sold a bubble that went on the front supposedly to increase mileage by smoothing out the air flow.
but what do you mean by wind deflector? those small jobbies that mount on the front of the hood, or one on the roof of a TV when towing a TT?
Oh I see somebody beat me to it. :)
bumpy