Fuel Economy Tip - Keep Your Tailgate Up
June 8th, 2006 | by Brian Carr |Today’s tip will probably come as a surprise to most of you, but will be especially useful for those of you who drive trucks.
Driving with your tailgate down doesn’t help you save gas.
I’ll be the first to admit, I bought into the notion that by having your truck’s tailgate down while you’re driving down the road (especially the highway) you would greatly increase your truck’s fuel economy. Apparently that just isn’t true.
According to several sites (Ask Yahoo! for example) state that you get roughly the same gas mileage driving with your tailgate up as you do when your tailgate is down.
According to the Ask Yahoo! article, this is the reason why:
“When the tailgate is raised, a “separated bubble” of stagnant air is formed in the bed of the pickup. Wind tends to swoosh over this bubble as though it were part of the truck. Lower the tailgate, and the bubble disappears, which leads to increased wind resistance.”
So, get rid of that net you used to replace your tailgate and go ahead and drive around with your tailgate up!
42 Responses to “Fuel Economy Tip - Keep Your Tailgate Up”
By penty on Jun 8, 2006 | Reply
good info, and had always wondered about that… well wondered about it to the extend that I never looked it up.
By Brian Carr on Jun 9, 2006 | Reply
Thanks, I’m glad I was able to finally post something you agree with!!
By transitive on Jun 14, 2006 | Reply
The Myth Busters prooved that tailgate up gets the best mileage.
By Lono on Jun 14, 2006 | Reply
This is great info. Not only did Mythbusters prove it, but so did the car guys years ago… and they both are MIT grads. Another important concern in the tailgate issue is that people look like tools when they do that. Even no tailgate is worse than a tailgate (sorry Pre-runner dudes)because the aerodynamics are very specific to the design.
I know it seems silly to discuss the aerodynamics of trucks… but I am on my fifth different type of truck and so am always up for learning
By Brian Carr on Jun 15, 2006 | Reply
Glad to hear I could help you out. I was actually really surprised when I came across this information.
By Travis on Sep 9, 2006 | Reply
I have researched this and I will admit that it is true to keep the tailgate up. But I would like someone to explain this. The times i did drive I would either keep the tailgate on or off (not down, off). Doing this would be the same thing as it down. But I really feel a difference. With it off, I can feel better acceleration and dips on the highway which i use every single day are smoother ( maybe less downforce). The speed also stays steady as well. With the tailgate on and I let the gas pedal go I slows down faster but with the tailgate off and release the gas pedal it doesn’t slow down as quickly. I notice these changes, when I’m usually going anywhere from 65 to 80 MPH.
I have a 2000 Chevrolet Silverado 1500
By Carl Gable on Sep 22, 2006 | Reply
Travis, you have a vivid imagination. I’m sure you ‘feel’ better with the gate off but the data does not support your perception. I think the answer to your questions would be better answered by a psychologist than a fluid dynamics expert.
If you want the full reasons see Society of Automotive Engineers: 2004-01-1146
Pickup Truck Aerodynamics - Keep Your Tailgate Up
SAE Technical Papers
Document Number: SP-1874
Title: Vehicle Aerodynamics 2004
If you really want to reduce drag, add a cover to the bed. See:
http://www.reubengathright.com/putruck20report.pdf
By Rob on Nov 15, 2006 | Reply
your hyper link to the reubengathright.com/putruck20report.pdf does not take you any where,…. I would love to read reports on the aero-d tests on this subject,… tail gates,..
By Travis on Feb 11, 2007 | Reply
I just want to thank all the people that helped the totally retarded insane rednecks of the world become better learnid about this. Thank you god.
By ngz on Apr 7, 2007 | Reply
While its probably true, I have a tonneu cover over my 1979 Elcamino
and even at 45 to 50 mph I notice the tarp being pushed down hard by
the air flow. It just seems as though if the tailgate were down the air
could simply exit the rear of the vehicle instaed of bouncing off the
tarp.
???
By Brian Carr on Apr 8, 2007 | Reply
ngz - thanks for the comment. To be perfectly honest, I can’t give you much of a scientific explanation, however, I’ve noticed that when I drive my father’s Ford F-150 with the tailgate down, the big rubber mat in the back tends to fly around, much less so than when the tailgate is up. I don’t know if that means there’s more air turbulence or not, just my observation…
By trucky on Apr 22, 2007 | Reply
This can’t be universal. I recall a specific example of a friend installing a mesh in place of the tailgate in an old (at the time) truck in the late 80’s. His top speed going up a relatively steep grade with a 45 mph speed limit was higher without the tailgate. It seems like in his case at least he was getting less drag with the tailgate out.
By Jz on May 8, 2007 | Reply
DO THE TEST CORRECTLY WITH THE TAILGATE “OFF”. I KNOW NO ONE THAT PUTS THE TAILGATE DOWN TO SAVE GAS. THEY ALL TAKE IT COMPLETELY OFF, THUS ELIMINATING THE DOWN FORCE THEY ARE SPEAKING OF. I.E. WEBBED TAILGATE REPLACEMENTS.
DO THE TEST AGAIN. I KNOW ZERO PEOPLE THAT LEAVE THE TAILGATE DOWN TO SAVE GAS. I KNOW MANY THAT TAKE IT COMPLETELY OFF AND REPLACE IT W/ A WEBBED TAILGATE. AGAIN, THIS ELIMINATES THE DOWN FORCE THAT WAS FOCUSED ON. THIS TEST WAS FLAWED.
By Jamie on May 23, 2007 | Reply
I saw an episode of Myth Busters just last night where they revisited this whole gas mileage thing about the tailgate. After doing the test again with the tailgate up and down to verify their previous results, they also tried 3 other methods fans had written to them about: Bed cover, no tailgate at all, and one of those mesh things. The bed cover results were essentially the same as the tailgate up, and no tailgate was basically the same as having the tailgate down. Surprisingly, or maybe not, depending on who you ask, the mesh provided the best gas mileage of all 3.
By John on Jun 28, 2007 | Reply
Well the mesh works the best for a couple of reasons. One, the mesh still helps to create the pocket of slow moving air in the bed of the truck which forces the air flowing over the truck past the end of the bed. Just like the tailgate up. Second the mesh weighs significantly less than a tailgate. Anytime you can reduce the weight of a vehicle you’ll improve gas mileage.
By Connie on Jun 28, 2007 | Reply
I have a 1984 El Camino. I’m thinking of getting a hard (fiber glass)tonneau cover for it. Does this help to save gas….getting a cover? I read what Jamie said above, but has it been PROVEN either way?
Thank you in advance for helping me!
Connie
By John on Jul 3, 2007 | Reply
Connie, the tonneau cover will reduce the drag on the truck from the wind resitence, but will add a significant amount of weight. You may actually notice a slight drop in gas milage.
By Sean on Jul 16, 2007 | Reply
Tailgate UP / Tailgate DOWN / Tailgate OFF
Makes no difference to gas mileage whatsoever. Ever wonder why NASCAR drivers have to touch bumpers in order to “draft” off the driver in front? Because the slipstream of the vehicle in front creates a pocket of air immediately behind the lead vehicle. The pocket of air carries back about 10 feet behind the lead car, allowing the following vehicle to drive with less wind resistance and thus conserve fuel.
A pickup truck usually creates all it’s wind resistance at the front of the vehicle. Air travels around the truck via the path of least resistance, well past the rear bumper, leaving the tailgate (or absence of) irrelevant.
TAILGATES MAKE NO DIFFERENCE AT ALL TO FUEL ECONOMY.
By Concerned American :-) on Jul 23, 2007 | Reply
The funny thing is all these posts and only 1 mention of the weight of the tailgate.
I have owned many, many trucks in my life and for anyone who has never done it, take it off sometime. You will be SHOCKED how heavy those things are. I had a full size Ford and weighed the tailgate at 75 lbs. According to standard rule of thumb that is 1.5% MPG improvement because of the weight reduction. If you that overcomes the drag change everyone talked about, then it is better off. If it doesnt, then It is better on.
Seems simple to me :-))
By jesse on Sep 2, 2007 | Reply
Mythbusters has done this myth twice. the first result was tailgait up is the best. The second time when they revisited it, the fount that mesh(not sure about the science behind that) was the most efficient, tailgate up second and so forth. Tailgate down was still the worst though.
By Jon on May 13, 2008 | Reply
Yeah, I’m sure the aerospace and automobile engineers would bow to the judgment of someone who uses all caps. YOUR BRAIN IS FLAWED.
By SBruce on Jun 3, 2008 | Reply
The article states; “Lower the tailgate, the bubble disappears, which leads to increased wind resistance.”
But why?? Why does a disappearing “bubble” lead to increased wind resistance? The air flows over the cab and down, the presence of an “air bubble” helps the air flow over and on its way back.
With no air bubble, the air flows over the cab, then instead of flowing over the bubble, it….what? It just continues to flow rearward with nothing to stop or impedes its flow of passing back.
Explain how this is or isn’t so???
By Anonymous on Jun 5, 2008 | Reply
dont talk about gas mileage if you drive a truck because you dont care, or you would have a honda
By Tonneau Covers on Jun 16, 2008 | Reply
I never really thought of it…but it makes sense it would save on gas due to air flow. Thanks for the great info!
By John on Jun 24, 2008 | Reply
Okay everyone. There are several things that must be considered in this equation. First of all there is weight. The more a vehicle weighs, the more the engine has to work to move it down the road resulting in fewer MPG. Removing the tailgate will reduce the weight of the truck and therefore improve gas mileage. However, weight is not all of the equation and therefore removing the tailgate alone does not produce the best results.
A truck is designed to have its best performance with the tailgate up. What is the science behind this? It is true and can easily be seen in wind tunnel testing that a “pocket” of slow circulating air forms in the bed of the truck as it moves down the road. Air passing over the cab “rides” on this pocket of air and is deflected over the back of the truck. Now, why is removing the tailgate all together not the best? After all the air will just flow right out the back, right? Well, almost. When there is no tailgate the air moving over the cab is allowed to flow into the bed of the truck. As the air “hits” the bed of the truck it creates drag and reduces gas mileage. In a similar way just lowering the tailgate provides and extended area for drag. In this scenario the tailgate acts like a spoiler pushing down on the back of the truck and increasing drag.
The best option is to remove the tailgate and install a mesh gate. Why you ask? The answer is the mesh gate does both things that will increase gas mileage. First, the mesh gate weighs significantly less than a tailgate which lowers the overall weight of the truck. Second the mesh gate allows for the pocket of air to form in the bed of the truck allowing the air flowing over the cab to “ride” this pocket over the back of the truck.
I hope this helps. I know gas prices are killers right now, but some of us rely on our trucks to make a living. No Honda can match what my truck does …
By dak5576 on Jun 27, 2008 | Reply
The nonsense in this discussion is amazing. And John, your comment about how a net retains this so-called drag reducing bubble is just illogical.
I haven’t seen the mythbusters, but from the comments here I gather that they contradicted themselves and got no conclusive results.
Not that I really care about the up/down argument, but I’m not buying that a bed cover makes zero difference, no way. It might not make much difference on a certain model truck traveling slightly downhill on a clear and calm night, but personal experience with my dak has shown a 2-3 mpg average increase with the cover.
So sorry to burst your ‘bubble’ but anyone who has driven a pickup truck at highway speeds with a little dirt/wood chips/straw still in the bed and paid attention would know thats not a ‘pocket of slow circulating air’, it’s more like a horizontal whirlwind.
And yeah, if you’re perceptive you can feel the increase in drag without a cover once you’re used to driving with one. Truck also handles a bit better if there are strong crosswinds.
With the cover on and a k&n filter my dak gets 20 or more mpg in local driving, have gotten 24 on the occasional long trip. Not bad for an old V6. YMMV, hah
By Anon on Jul 12, 2008 | Reply
The best way to go is to take the tailgate off and replace the tailgate with a mesh gate.
By Sean in CA on Jul 13, 2008 | Reply
HAHA! I used to think most people with their tailgates down and / or with mesh nets were morons. Now that I’ve read a majority of these posts, I can confirm that is the case.
By Anonymous on Aug 8, 2008 | Reply
well said
By Rainer1 on Sep 8, 2008 | Reply
Just wondering why nobody has pictures with the “smoke” streams like they show in the wind tunnel pictures of cars being tested. I once had a Styrofoam coffee cup “float” in my rear view mirror (tailgate up)for quite a distance. Speed was about 50 mph. The cup finally dropped to the bed and stayed against the tailgate. I assumed the air pocket and flow created this odd occurrence.
By Adam on Sep 9, 2008 | Reply
So this can be put to rest.
Dodge Ram 1500, Ford F150, Ford F350, Chevy Silverado.
Range from 05-07
Trucks were done in controled simulations with;
Tailgate On and Up, Tailgate Off, Tailgate Down, Mesh Net Instead of Gate, Metal Cover on box, Soft Cover on box.
IN ALL TESTS !!!
All trucks showed less wind distrubance with tailgates on and in up then any other.
Smoke line followed from top of roof in a downward degree to the end of the truck.
Reason - Starting speed, wind is forced into the truck bed, it fills but is unable to get out due to much higher velocity air going over it. This acts like a smooth surface for the air to ride over.
Test Results In Order From Best To Worse, In Best Aerodynamics and least Air Turbulence;
1) Tailgate Up
2) Tailgate Up - Metal Cover
3) Tailgate Up - Softcover(Not tested on Ram1500)
4-5) Tailgate Down/Off Depending at speeds, the tailgate being down would start to cause incressed amounts of downforce and drag. This would give a higher amount of workload to a engine, thus increassing fuel consumption.
7) Net - This rated last due to the fact at speeds of 60MPH-90MPH, the net started to act like a parachute. This caused the worst in all tests.
Tests were done in a wind tunnel, with wind speeds rating from 40 to 100MPH, Each test per truck was done 5 times, with the Avg of all 5 used. Trucks were judged on smoke lines from both sides of truck as well as back.
Hope this puts it to rest.
By Bill on Sep 11, 2008 | Reply
I feel the same easier rolling sensation with the tail gate down. I’ll be the gas companies are making up the myth-buster.
By Kid Stevens on Jan 2, 2009 | Reply
?Then explain why a coke can set on top of a Ford truck cab then released will hit the tailgate 6 inches down from the top.. If the can hits that point the wind hits that point. The wind pushed the can there. If there was a bubble of air in the back then the can would have rode on the bubble. This can trick works from 30 mph and up even at 100 the can hits inside the bed. If you try that with a Ranger or an early short wheel base F-100 the can missed the tailgate by several inches.
By Kid Stevens on Jan 2, 2009 | Reply
If you got a net it shows where the wind is, the net is shoved back at speed. If there was a bubble of air in front of it the air sliding over the would only bend the top of the mesh gate. If the mesh gate is shoved back by air flow over the cab there is then the same air hitting the solid tailgate.
By Sean in CA on Jan 3, 2009 | Reply
RE: The Coke Can Test.
If I drop a Coke can from a second story window, it will hit the ground. The phenomenon you’re describing is called gravity. It’s all relative to the speed the vehicle is travelling at and the weight of the object dropped. Any bubble of air that relates to fuel economy starts at the front of the truck, not the roof of the cab. Place a can on the hood and then see where it ends up. Odds are it’ll clear the bed by 100′ at highway speeds. Better yet, stick about 20′ of landscaping tape to the leading edge of the hood and then drive. Watch where the tape goes. Good luck.
By Kid Stevens on Jan 4, 2009 | Reply
You didn’t read very well It works from 30 mph to 100 mph. I know how air flow works. Do you work in a wind tunnel? I used to.
By Alex on Jan 4, 2009 | Reply
Kid, you don’t get it. There is a much larger airflow that is created by the hood of the truck, not the roof. Granted, air does flow over the roof and into and over the bed, but the amount of drag this airflow creates is inconsequential in terms of fuel economy. The largest area of drag is created by the grille and hood. The windshield acts as a ramp, pushing this highly resistant air up, over and behind the truck. A slight, venturi type effect can be felt in the bed, but as I said before, it (the bed) has no effect on fuel economy whatsoever.
PS: In anticipation of your follow-up, I have worked in wind tunnel testing for the US Cycling team in both Colorado Springs and San Diego.