Remember when the new style GM/Chevy trucks came out with the wide shelf molding on the top of the tailgate? Notice how the Fords are similar now (not as wide)? The theory is the shape of the molding has a lot to do with how the air flows over the back of the vehicle. It is supposed to actually cause some turbulance and the force of the wind ends up comming back to the gate and "pushes" the truck. One would think the air flows over the cab and drops directly into the box causing drag, evidently that is only minimal. I would imagine you would save some gas removing the tailgate, since the thing weighs so much.

 

Hey Folks, I Like The Rest Of You, I Would Like To Get Better Mileage With My Screw But That Was Not My Concern When I Bought It, If So I Wouldn't Have Done So.
As Far As The Tailgate Off Or On I Can't Answer But I Will Suggest Leave The Gate On And Up. Have You Ever Looked At A Truck That's 4 Or 5 Years Old With Out A Tailgate? The Gate Helps Support The Bed Sides And Without It The Sides Will Shake And Eventually Break Loose At The Bed Floor Where The Tailgate Should Be.
I Saw This On Several Of My Frields Trucks Back When Those Tailgate Nets Were So Popular.
Plus I Think A Truck Looks Stupid Without The Gate. You Wouldn't Drive It Without The Fenders So Why Remove This Body Panel Just Because You Can.
Just My Opinion On The Matter.

 

I drove an 87 Nissan for 11 years with a 5 speed transmission. I averaged around 25 to 26 mpg...tailgate in either position. I added a fiberglass bed topper and my mpg then averaged 30 to 31 mpg.
With my 97 F150 with a 4.6 v8 and auto transmission.....I see no difference in mpg with tailgate up or down.
That's my 7 cents worth!

 

Not only is it uphill going and downhill coming back, but the wind is almost always at least somewhat from the west. I make the trip from Lincoln, NE to Dillon, CO every winter to hit the slopes. We usually have 3 vehicles, and we always get much better mileage coming back, even after a the halfway fill coming back, we're still getting better mileage than the first half of the drive out there. With my wifes car it's a difference of 24 MPG going to 28 MPG coming back.
As far as tailgate up or down, I've read "scientific studies" that prove both. So believe whichever you want. Here's my experience. I average .5-1 MPG better with the tailgate down. I can get as much as 19 MPG at 75 MPH with it down , and get 18-18.5 with it up.

 

It's been common knowledge since at least the 70's that tailgate down or no tailgate will improve the mileage in a lot of trucks noticably. In fact, for years it was common in parts of the South near where I was raised for people to drive with their tailgates down all the time. You can usually tell someone who has done it for years. The top of their tailgate is smashed in either from backing into something, or from someone hitting it.

A tonneau cover eliminates the tailgate up drag, looks better and keeps the contents of your bed dry and out of the sun.

I've personally never understood toppers. You buy a truck and then put a permanent cover on it?! Why not just get a station wagon or Suburban?

 

The basic aerodynamics of the pickup bed are such that the airflow fills the bed and the cushion of air causes the air flowing over the cab to be pushed out of the bed. It's exactly like ground effect in aircraft. Open the gate and the cushion goes away.

 

http://hyperphysics.phy-astr.gsu.edu/hbase/pber.html
Shows (down near the bottom) the drag changing by changing the angle, or the speed. No matter how effective the tailgate would be at inducing turbulence to break up drag, that effectiveness would vary in direct proportion to it's speed. Both up and down. So it might work at one speed, but it would not work at a different speed.
Even if Ford (or whoever) designed the tailgate to break turbulence, it would only be at a certain speed. It would create turbulence at different speeds.

This would also be true of running with the tailgate down. At certain speeds it would INCREASE the drag. But at others it would decrease it.

One flaw in all the arguments about the designers building the tailgate for better airflow;
It ain't ever going to happen.
The people who make the decisions for the final design are not scientists or engineers, and they DON'T like, respect, or care about those who are. They are marketing experts and bean counters. Cosmetics, sale ability, and cost. Nothing else matters.

And Lets face it, how many of us bought these trucks based on anything but Marketing, Cosmetics, and Perceived value.
Would you have bought your excellent looking truck, if it had had a seven inch higher or lower tailgate? Which would make it look 'a little odd'. Even if it had saved you 1 or 2 mpg on the highway?
Note the proof is in the deeper bed on our trucks. NOT one word in the marketing mentions that if the bed was shallower, the mileage would be better. No, they put the deeper bed in because a competitor had a larger capacity in their advertising.

I'm not complaining, It's the free market. I could have bought a mini-truck... I have owned a dozen of them over the years. This time I wanted a full size one.
And I could buy it. I like the free market.

For those who want the better mileage, and don't want the weight of a fiberglass tonneau, try a hard aluminum cover. My Fold-a-cove is light enough my wife can carry the four panels by herself, and it seems to help my highway mileage more than a little.
To each his own.
Chris

 

Because I am a musician....I carry my drums in the back and it keeps them dry if it's raining. Topper comes off easy enough if I need to carry anything of any size and I hate any type of SUV or station wagon.

 

Yeah, but without the topper, you could play your drums in the back or your truck. Your limiting your opportunities here.

 

A truck is supposed to have an open bed. If you want it closed by a grocery gettin Expedition.

 

well said.......

 

In Road & Track magazine there was a brief story in the tech section on this very question (gate up vs. gate down mileage). I think it was a couple of months or so back. The article cited wind tunnel tests that were done and the conclusions were that having the gate down actually hurt mileage.I think it also mentioned the improvements typically seen when the bed was covered with a hard tonneau cover. As I recall it was a very well written piece.

I've got a Snugtop SL tonneau on my Lariat S'Crew and it has helped a bit but overall my mileage is still so-so.

 

To each his own.

 

A very closed minded statement. Just because you don't have a need for a topper, doesn't mean that a truck is supposed to be that way. Some people need a topper so they can keep things locked up or out of the weather. I prefer an open box, but have used trucks with toppers and they are very handy for hauling furniture when it's raining, and can also double as a tent while on campiing trips, yet you don't ruin the seats upholstry when you need to throw a freshly shot deer carcass in it.
Like ddrummna2004 said:
"To each his own,"
just don't bash others because you have different needs. Grow up.

 

AG4.0

Although you make a good point about difference, you too left a little slag with your "grow up" statement.

Toppers are here for those who need them, just as are tonneaus, bed liners, grill guards, mud flaps and fuzzy dice.

I restore cars and trucks to factory stock, some think that is boring, others think it is proper.

Heck, I agonized over the color of my latest purchase before I made a decision. Actually, KBB and others make no distinction of value concerning color (unless it is a premium paint), so it is a matter of customer choice.

Just a matter of preference