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I spent a lot of time last winter reading everything that I could find regarding trailer aerodynamics and things that I could do to improve the overall fuel economy of our rig.  My truck is not that efficient to begin with,(19 mpg. at its best)  and I was sweating the great unknown of towing out west in the spring.  The first thing that I considered  was a wind deflector like you see on trucks towing bigger trailers.   The general consensus regarding them , and for that matter anything you would mount to your tow vehicle is that they would have to be mounted within a foot or so of the trailer to do any good at all.  Then even under optimal conditions the fuel savings would never add up to the cost of the units.  The next thing I found was that  you have to treat the trailer like it is on its own traveling beside you.    A brick on wheels can never have a Lamborghini coefficient of drag however surely there was some room for improvement.   I then read that improvements could be made by streamlining the undercarriage of the trailer, which the factory took care of for us with the black material under there.   Rounding the surfaces like an airstream helps, but I did not buy an airstream, and would not even if I could have afforded one.  There are nosecones that you can buy that promised improvement, but they too were expensive and change the look of the trailer.  Then there was talk about the drag caused by air collapsing around the rear of the trailer and work done by the trucking industry  and others (in my case, nasa) to improve airflow back there.  We have all seen this sort of thing by now in one form or the other.  That’s what you are seeing  (and sometimes not seeing) on the backs of big rigs all across the country now.  The most obvious are the three or four sided tapered sails attached to their backs.  Less obvious are metal bars welded at  odd angles on the tops and sides of the  trailer. The intent of these devices are  to reduce the low pressure (suction)drag by  guiding the air coming around the trailer  in such a way that it reduces the suction.   The theories involved here are hard to follow, lots of talk about vortices and such.   I found a product that claimed to be developed by nasa and bought into it.  For a sum of money less than any wind deflector or nose cone I got a small box with about 30 of these plastic stick-ons (you can see them in my pictures).  I am not endorsing these because I just don’t,  so they remain nameless. 

My experience with these have been good, however I cant for certain say they have improved fuel economy. I have gotten as good as 14.5mpg on i59 (flat and still air) to 6.9 mpg on i10 (Texas high country with "I cant open my door in this" wind) I can say they have dramatically improved the driving with the brakes on feeling that I had before, and when big truck pass (25+mph faster than me) there is very little of that pulling to than pushing away sway (or vise versa) that I had before.   I have driven at least 5k miles since installing these.  I have been sway less except for one stretch of  highway between page az. And flagstaff where we had a crosswind that tried to push us over a couple of times.  That made it worth it to me

Post edited 3:57 am – October 8, 2012 by ron_sue

anyway, when i do the math all this is really not gaining much.  for my truck empty, traveling 1000 miles the best i can hope for is using around 52 gallons of gasoline. under most conditions with the trailer 80 gallons.  i have a 21 gallon tank so that's just over a tanks worth of savings potential at best, four vs. three. (and that would be impossible just from the weight addition alone).  we rarely venture more than 400 miles or so from home,( you are about a thousand miles from here, that radius gets me most of the country) so i cant get crazy with modifications.   the tabs only hinted at a 4% increase ( .5 mpg maybe) but i thought "who knows".  they  do seem to help with the truck induced sway (at least in my mind) and its a conversation starter for people who have looked out a window at a freeway, or watched their own wake in the rain. 

most of the time, we can go out for a week, eat our own gourmet cooking, see and do things that most only dream of, then collapse in our own bed every night for the cost of one or two nights at the Ham***on.  so as the old song says "that's close enough to perfect for me"