RV wind deflectors????????

I'm not sure the benefit of a wind deflector. Seems most trailers already have streamlined nosecaps and the wind deflector on the truck isn't needed.

That is why I am asking. We are taking some longer trips and looking to get better than 8 MPG

On pickups, the cab-to-trailer gap is generally too large for a wind deflector to realize any benefit. It may even make aero worse, since the air coming off the wing will likely crash into the front of the trailer, rather that going over it. But then you now have another low-pressure zone behind the wing adding drag.

Minimizing the cab-trailer gap, and cleaning up the air coming off the back of the trailer are probably the two easiest things to do. After that, you have to look at minimizing the air going under the front of the truck (which is why the Freightliner New Cascadia is only a few inches off the pavement), then keep it from getting sucked under the sides.

They are not "snake oil", properly set up they will improve your mileage. I ran one, can't remember the brand, for 3.5 years mounted on the rear of my Leer Shell on an F-150 SCab towing a 22' 5,600# TT. It worked very well gaining me 1.5 to 2 additional mpg. This paid the $350 purchase price back in a year.

As noted I believe the key to my success was the fact that it was mounted at the rear of the truck, closing the gap with the front of the trailer. It only took a couple of minutes to mount and was very secure with no additional wind noise. Of course, I only ran it when towing.

We logged about 15,000 miles a year with this setup and I never had a negative experience and the mileage improvement was amazingly consistent {I always ran with my Scan Guage documenting/supplementing my pump calculations.}

Here is a shot taken at Quartzsite 8 years ago:

Moderator edit to re-size picture to forum recommended limit of 640px maximum width.

:C

carringb wrote:
On pickups, the cab-to-trailer gap is generally too large for a wind deflector to realize any benefit. It may even make aero worse, since the air coming off the wing will likely crash into the front of the trailer, rather that going over it. But then you now have another low-pressure zone behind the wing adding drag.

This is exactly correct.

Also think about the additional wind resistance that deflector will cause when you drive round without the trailer attached.

Safe your money; don't buy snake oil.

Looks aside, not sure what these things go for but you have to figure out realistically how many miles would you have to drive to hit a break even point?

1.5 to 2 mpg improvement? That's hard to believe.

carringb wrote:
On pickups, the cab-to-trailer gap is generally too large for a wind deflector to realize any benefit. It may even make aero worse, since the air coming off the wing will likely crash into the front of the trailer, rather that going over it. But then you now have another low-pressure zone behind the wing adding drag.

Minimizing the cab-trailer gap, and cleaning up the air coming off the back of the trailer are probably the two easiest things to do. After that, you have to look at minimizing the air going under the front of the truck (which is why the Freightliner New Cascadia is only a few inches off the pavement), then keep it from getting sucked under the sides.

I have never ran a wing on my truck nor will I ever. I have raced cars for over 40 years and have learned somethings about aero over the years.

The things I have learned over the years about aero are pretty much condensed into what Bryan has typed.

The two big problems are air getting under the truck and trailer and the air trying to get in back of the wing just as Bryan has said. One more big deal is the air trying to suck the trailer backwards after it passes the back of the trailer. IOW's the back of the trailer is every bit as important as the front of the trailer.

A really smart guy a very long time ago by the name of Aristotle once said: "Nature abhors a vacuum." He was absolutely correct. Air is very sneaky! If you keep it from out under your truck, it wants to sneak back in. Hence the reason for side skirts on race cars.

One thing that does work (ever so slightly) is air tabs. They help by taking some of the vacuum away from the back of the trailer. Unless you full time many, many, many miles a year you will never get your money back on any of this stuff.

If I had to sum it up about wings on a pickup truck pulling a TT it's like putting lipstick on a pig. To some people the pig looks pretty with a nice shade of lipstick on. But to people in the know, they just look at the pig and say, "it's still just a pig wearing lipstick."

9000# F350 4x4 towing 13,000 5th wheel.
Air deflector on cab of truck improve your mileage......NOPE


Towing at 62 mph would make better MPH then air deflector
And if already towing at that speed then you might want to have engine diagnostic done (8 mpg/diesel IS low....if GAS---then it is what it is)

I love people that have these and they drive around BobTail with the wing up.