Have been using them since Oct of last year and like them alot. The fuel savings has been hard to track, we installed rear centramatics, new rear shocks and new steers at the same time. We also went into winter diesel and Howes about the same time.
I find that if I get a little fuel savings, it's either gobbled up by pushing the truck for a tight load, or sustained by keeping my foot off the throttle.
But they do very well with buffeting and rear visibility. It seems that with a very strong crosswind the truck doesn't react as wildly, it's slipping thru that wind gust.
And the claim about the rain being skirted down behind the truck is accurate for us. It's especially noticable when changing lanes in blowing snow! I can actually see the lane behind me. The cheap price is worth that feature by itself.
The Gibster