Wind deflectors

[bizzaro]

Does anyone know if those wind deflectors have any effect on gas mileage .. Will these deflectors give you better gas mileage and if so how much

[christopherglen]

For a SUV or pickup with a shell, putting the deflector all the way back can net decent mpgs, 5ers are so far from the cab wall (VS height above cab roof) it is near impossible to gain beyond a few tenths of a mpg. Most people can save that much by slowing down 2-3 mph.

[Community Alumni]

In order for a wind deflector to be effective, it has to be mounted to the trailer as close as possible, like within a few feet, and it has to be angled properly or it will create additional drag. The problem is that most setups don't allow for mounting in a place for the deflector to become effective to begin with. The trailer gap is much too large and exposed. What ends up happening is that part or all of the airflow falls off the edge of the deflector and down into the trailer gap where it becomes drag. Also the deflectors are not large enough. There's just not enough surface area to adequately deflect enough of the airflow. When faced with a 96" wide trailer cap, a 48" deflector can only address half of the airflow over the top the trailer in a perfect world. The other 48" is out in the open. The deflectors only address a small amount of airflow going to the trailer. There's still tons of airflow hitting the exposed sections of the trailer and entering the exposed trailer gap. All of this air entering the gap creates a turbulent flow which creates drag. At the end of the day deflectors ends up being mostly ineffective. Most who've tried will tell you that they are not worth their money, unless you need a really expensive bug shield. If you could seal the trailer gap then that would have a much greater impact.

On the other hand, modern semis have a much better design than our combos. They have huge condo sleepers that meet both the height and width of the trailer. The top of the sleeper end up becoming a quite effective wind deflector. There's several inches of additional side fairings behind the sleeper. This works as vertical deflectors, redirecting air around the gap and to the trailer sides. You end up with a trailer gap that experiences very little airflow and almost eliminating 25% of the drag the unit experiences while traveling down the road.

[beemerphile1]

Only a wind tunnel knows for sure, personal experience is extremely unreliable and essentially worthless. Without scientific/wind tunnel testing, we will never know.

People claim from personal experience that fuel line magnets and deer whistles work, but lab tests have proven that they don't.

[Passin_Thru]

I ran to Oklahoma,a and back to VA and got 9.5 going out and 10.8 coming back and I don't have one. Prevailing winds IMHO.

[SprinklerMan]

dodge guy wrote:
I just got mine this year. I found it on CL for $75. It is adj.

I used to get around 6.5 mpg so I figured any little bit would help! Well On our first trip I got 8.5 mpg!!!! I had to recheck my math and the miles. It was for real. The only other difference was new tires on my X (I went from BFG A/T to a more hwy friendly tire), but even with that my mileage without the wing was similar. I even rechecked on the way home and again it was 8.3! And then on our Myrtle Beach trip I averaged 7.9mpg with the mountains I went through out east! By my math I saved approx. $200 on that trip alone!

I also noticed the truck doesn't work as hard to hold speed. It use to kick out of O/D on the slightest hill or headwind! Now it just keeps on pulling until I'm really into the throttle. The key is having the deflector as close to the trailer as possible and at the right angle.



For me, I see excellent results from it's use!

I have basically the same set up with my excursion v 10 , and my results were pretty much the same .

[dodge_guy]

I just got mine this year. I found it on CL for $75. It is adj.

I used to get around 6.5 mpg so I figured any little bit would help! Well On our first trip I got 8.5 mpg!!!! I had to recheck my math and the miles. It was for real. The only other difference was new tires on my X (I went from BFG A/T to a more hwy friendly tire), but even with that my mileage without the wing was similar. I even rechecked on the way home and again it was 8.3! And then on our Myrtle Beach trip I averaged 7.9mpg with the mountains I went through out east! By my math I saved approx. $200 on that trip alone!

I also noticed the truck doesn't work as hard to hold speed. It use to kick out of O/D on the slightest hill or headwind! Now it just keeps on pulling until I'm really into the throttle. The key is having the deflector as close to the trailer as possible and at the right angle.





For me, I see excellent results from it's use!

[Beer_Belly]

Beer Belly wrote:
gotta admit though....those things look cool

I thought you were talking about the big chrome wing

[mlts22]

Turtle n Peeps wrote:
Next to nothing. What people don't understand is that the back of the trailer if just as important as the front.

This is exactly why the 18 wheeler hauling companies are using those "fish mouth" things that go on the back on their trailers.

[Turtle_n_Peeps]

Next to nothing. What people don't understand is that the back of the trailer if just as important as the front.

[rockhillmanor]

bizzaro wrote:
Was unable to open link

Here try it now.

This is the link to RV'er who installed one and gives the specs he received regarding mpg, how to install one, pixs, etc. after putting one on.
And there are several more RV'ers feed back too.

http://www.ford-trucks.com/forums/1057241-rooftop-air-deflector-towing-travel-trailer.html

[Peg_Leg]

As far as fuel savings, I never really saw any advantage that could be deemed as savings. With weather conditions different on each trip it would be hard to determine cause and effect for the device.

I have and use a second hand deflector on my 5er. At a cost of $60 I could justify it at least to myself. I had a diy deflector mounted on top of a shell at the rear with my old TT setup. I felt less turbulence with the TT, the stability increase with a SRW truck and TT made it worth having. With the 5er and a dually truck stability is not an issue.

As stated above the kamikaze critters miss their target more often and have to look for another battleship. The only downside is the surviving bugs are still able to reproduce.

[skipnchar]

In order to get any SIGNIFICANT difference you'll need a very LARGE deflector. I used to travel with my 8 foot bed cover (solid fiberglass) propped open, giving me a 4'X8' wind deflector and got a couple of miles per gallon improvement in towing my 34 footer with the 5.4 V8 engine. For the MOST part it's not practical to drive around with that much deflector and much less will of course return much less. It will be hard to justify the cost unless you get a VERY good deal on the deflector (my cover cost me over $800.00) but I had it anyway to cover gear in the truck (which it no longer did when it's propped open) 🙂

AS for a "topper" they might possibly improve wind resistance a little bit but you'll also be hauling more weight so my best estimate is they're about a push. A TONNEAU cover will NOT increase your mileage any measurable amount as you no longer get the vacuum effect of an open bed with tail gate closed, which is proven to be the MOST economical but the differences are minimal.
Good luck / Skip

[prichardson]

It depends on the rig. From experience - I had a TT with a vertical front and towed with a short bed pickup. With a deflector I gained 1 MPG. My current TT has a front that slopes apx. 20 degrees off vertical and with the same truck and deflector the gain is minimal.

[Beer_Belly]

gotta admit though....those things look cool