Tailgates and fuel mileage???

[JHardwick]

Does anybody have any hard data on fuel mileage with/without a tailgate while towing either an enclosed goose or 5'er?



I know that with my enclosed goose, I have to be careful of what I put in the bed, or it'll be gone! I've had cooler lids blow open, half bales of hay blow out etc ... ... ... ... . it seem that there is a lot of turbulent air in the box that could be vented with no gate/air gate.



With no trailer, the air in the bed becomes basically "dead", but that's not the case with a nose over type of trailer.

 

[DeezelDood]

"Myth Busters" did a segment on this subject a while back. They calculated that tailgate down actually led to worse mileage than tailgate up. I don't recall if they tried it with the tailgate off. Purely by cooincidence (I'm not that anal) I drove my truck for 5k miles (90% fwy) with the tailgate up. Bone stock, brand new. I drove the same route, same speed, for another 5k miles with a Leer shell. Engine was broken in a bit, I should have seen improved mileage. Mileage dropped about . 75 to 1 mpg. The camper shell weighs about 200 lbs. The extra weight obviously hurt more than the theoretical reduction in drag, but should not have dropped that much. I'm inclined to believe that all things equal (camper shell=zero wt) that I woud see better mileage with the open bed, tailgate up.

 

[JHardwick]

I'm not interested in mileage differences without a trailer, I cover 100,000 miles a year with a trailer.

 

[Grizzly]

I have not seen any difference in fuel mileage either way, however many years ago when I purchased my first 5er, a 29' 1988 Holiday Rambler, which I pulled with my Furd gas engine F250, I had quite a bit of turbulence on my first trip with the standard equipped tailage. I then installed a "V" notched vented tailgate. No more turbulence. On the other hand, with my 05 Dodge and the new Arctic Fox 5er I have no turbulence with the standard equipped tailgate. I can't explain why the Furd had it and the Dodge does not.

 

[Forrest Nearing]

why don't you do it for 20k miles and report back. I'd say you're the perfect test bed!

 

[JHardwick]

I keep threatening to. In fact, I'm leaving Monday on an 11,000 miler.

 

[JHardwick]

Grizzly:



Sounds like this may be a deal where different truck/trailer combinations may/may not see a benefit.

 

[DonTX]

I am now towing with the old tailgate that used to belong to Grizzly, there is no turbulance in the bed with it with my setup. On some board once there was some sort of a test, that indicated that with a 5er you were better to have a vented or no tailgate. It was theorized that the shape of the fifth wheel put more air in the bed, and the tailgate became a resistance.

 

[JHardwick]

It was theorized that the shape of the fifth wheel put more air in the bed, and the tailgate became a resistance.

That's kinda what I had in mind. I was traveling 70mph with a huge head wind once, and looked in my rear view to see a bale of hay pinned up against the under side of the goose neck. I'm thinking that with no tailgate, that air could spill out.

 

[CUMMINZ]

Think of all the extra weight you are hauling around with all that turbulance:-laf

 

[JHardwick]

Think of all the extra weight you are hauling around with all that turbulance:-laf

explain, I'm all ears ... ... ... ... ... ... ...

 

[jimnance]

I've seen the turbulence created in the bed of my Dodge when pulling my fifth wheel and stock tailgate. When a louvered gate was installed turbulence was greatly reduced.



It takes energy to create turbulence, so my guess is that reduced turbulence would result in better efficiency. I don't know how significant it would be. There are so many other variables involved when I haul, I can't honestly say I've seen any mileage difference. I suspect whatever it may be it will be minor compared to say slowing down 5 MPH.

 

[Cattletrkr]

W/O a tailgate, is the turbulance gone, or just gone from the bed. That air has to be going somewhere. My guess would be it's still there at the front of the trailer, swirling around doing its thing.

I just bought a 3500 C+C so now I have a flatbed for the first time ever. My mileage is down, but i'm attributing that to the engnie being new. MPG's are actually higher than the '04. 5 was when it was new. All that means is that I don't think I'm losing any mileage with a flatbed, but I might be gaining. Too many variables to know for sure though.

 

[Grizzly]

I've seen the turbulence created in the bed of my Dodge when pulling my fifth wheel and stock tailgate. When a louvered gate was installed turbulence was greatly reduced.



It takes energy to create turbulence, so my guess is that reduced turbulence would result in better efficiency. I don't know how significant it would be. There are so many other variables involved when I haul, I can't honestly say I've seen any mileage difference. I suspect whatever it may be it will be minor compared to say slowing down 5 MPH.

What I'm starting to think now is that perhaps the turbulence is created by the design and shape of the 5th wheel. On a 1500 mile trip with the stock tailgate and the new Arctic Fox 5er, I had no turbulence. With my 95 Dodge/Cummins and my 88, 29' Holiday Rambler, sold in 98, and with the stock tailgate, I had a lot of turbulence. The V notch vented, chrome tailgate didn't fit my 05 Dodge. Don/TX now owns it.

 

[DonTX]

Your experience mirrors that of a friend of mine, pulling a 5er with a 1500 gas Chevrolet. He changed brand of trailer recently and it made a noticeable difference in his fuel mileage, even though the replacement trailer was as heavy. He is certain that the frontal shape of the 5er made a world of difference. I have not pulled mine with the stock tailgate so cannot compare. With the open air tailgate, I can leave all sorts of loose items in the bed, nothing moves.

I wish fifth wheel makers would do some aerodynamic tests, i think there is room for some imporvement.

 

[CUMMINZ]

We are planning about 6k miles starting the end of May to the west. I just placed my 5er tailgate back on the truck. I am sure it helps. I have noticed the turbulence in the back with the factory gate.

 

[DonTX]

A few years back I took my Dodge PU to the Sears store to pick up a gas kitchen range I had ordered. While flying down US 160 with the tailgate up, I noticed in the rear view the box "floating" off the range (I thought). Pretty soon it came up and over and landed in the center of the highway! The suction is so great, it lifted that range out of the truck, box and all and went sliding down the highway! I learned from that!

 

[DeezelDood]

I'm not interested in mileage differences without a trailer, I cover 100,000 miles a year with a trailer.

Aerodynamics

 

[Jumbo Jet]

Best MPG I ever got on my Dodge CTD was from Fayetteville, AR to Sevierville, TN to pickup a Lance Truck Camper. I left the tailgate at home and drove above the speed limit.

There may be a point of diminishing returns, or a point where the absence of a tailgate actually reduces drag thereby increasing fuel mileage.

I am not knocking Myth Busters, but my own experience proved different.

I run a louvered tailgate 95% of the time just to reduce turbulence in the bed. I have had a HEAVY rubber mat slap the rear of the cab from turbulence when the OEM tailgate was up.

BTW - I have never driven my Dodge CTD over 115 MPH.

 

[Grizzly]

Best MPG I ever got on my Dodge CTD was from Fayetteville, AR to Sevierville, TN to pickup a Lance Truck Camper. I left the tailgate at home and drove above the speed limit.

There may be a point of diminishing returns, or a point where the absence of a tailgate actually reduces drag thereby increasing fuel mileage.

I am not knocking Myth Busters, but my own experience proved different.

I run a louvered tailgate 95% of the time just to reduce turbulence in the bed. I have had a HEAVY rubber mat slap the rear of the cab from turbulence when the OEM tailgate was up.

BTW - I have never driven my Dodge CTD over 115 MPH.

I had the same experience when I drove my 95 to St. George, Utah to pick up my 98 Lance camper without the tailgate. From Albuquerque to St. George, I got 22 mpg, which was my best mileage ever.



A few to several year back, Consumer Reports wrote an article on the fuel mileage with the tailgate up and with the tailgate down. Their findings were that it made no noticeable difference. I'm here to say that, I don't belive their findings are accurate. I believe that the tailgate off, down or a vented make a big difference.