Tailgate Up or Down – Explained

Is it better for gas mileage to leave your tailgate up or down when driving? This video explained the fluid dynamics, and gives you the answer!

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46 thoughts on “Tailgate Up or Down – Explained

  1. Vernon Ray says:

    What happens with a tounnier cover on

  2. Rob Grune says:

    will a truck cap improve fuel economy?

  3. matt sword says:

    Please do a updated video on this topic and add in ,if the tailgate completely off (weight savings) is better mileage or not please. I’m trying to figure out if I take my tailgate off at the drag strip will increase or decrease my 1/4mile times. I kno you said it’s better to keep it up for mpg but I’m curious if taking it completely off and saving some weight is better or not. My tailgate has the locking and unlocking ability so it weighs roughly 55-65lbs I’m just wondering. Ty

  4. Paul Smith says:

    He's drawing the circulation in the wrong direction at :43.

  5. like your vids, very instructive. Can you make a video on the additional drag caused by having a matt or satin finish paint vs gloss and/or polished surface

  6. what about long bed pick up trucks

  7. Sorry, but it's not that black and white. There must be a speed variable you haven't tested. I get 21 mpg with tailgate down vs 20 mpg with it up at 70mph speeds on the interstate during 150 mile runs. The vehicle is a 2001 Chevy Silverado with 5.3 litre Vortec and 3:73 gearing.

  8. Shane Mirey says:

    What about net tailgates? Would they still have the same effect as a solid gate?

  9. Thanks for clearing that up for all the rednecks! ;)

  10. Akash Nigam says:

    hey can anyone get me some mathematical theoretical proof of that air bubble thing. Then I would be fully satisfied

  11. Bill F says:

    What about a Tonneau cover, you have weight gain vs improved aero… that would be an interesting thing to see examined and explained.

  12. commando_qt says:

    How about when I am racing (the tailgate up or down)

  13. Andy Gomez says:

    Wouldn't the turbulent air flow help in balancing the force of head-on drag?  Keeping the tail up would create that deadspace that would act as a vacuum slowing down your truck and reducing gas mileage.

  14. RM G says:

    how about with the tailgate off? (detached) Will the down-force on the truck bed waste more gas vs the tailgate attached and facing up?

  15. janderro says:

    is this wind tunnel approved? I have driven an '11 tacoma some time now, and I can tell there is a little fuel economy difference when reaching 90-100mph speeds. I can say that I get better economy with tailgate down.

  16. lizzardlife says:

    does this work the same with long beds as well as short beds?  standard cab vs extended cab?  where can I get more details? 

  17. Tailgate up sure for double cab truck,
    but I have single cab model,
    so the tailgate is too far from the cabin and the air is down to tailgate.
    I will try to test my truck, about the acceleration on high speeds with up and down to see the time results 

  18. Gumba Sal says:

    how about tannau covers and truck caps?

  19. Having your windows down will increase your drag, so it will negatively affect your fuel economy.

  20. Andy Wolf says:

    What if you have all windows down, including the back? It would seem I get better fuel economy in that scenario with the tailgate down.

  21. jabootydah says:

    mileage depends heavily on what type of driving you are doing. too many variables to blame it on the tailgate when only doing one or two tanks of fuel

  22. jabootydah says:

    what about in a drag race?

  23. steve71123 says:

    after hearing the car talk guys on leaving the tailgate down will get better mileage. this is completely wrong. after experimenting with my tacoma truck for one tank of of gas my mileage is down an average of 2 mpg.

  24. Oranger37 says:

    "this throws my entire perception of reality in into question"

  25. 7150285 says:

    is your hatchback a diesel? Black smokes accumulates (black dust) which is basically unburnt diesel fuel.
    As for hatchback or station wagons, I am just assuming it is just a little "not by much" less aerodynamic than sedans because of drag. Don't know if u know much about guns but a boat-tail bullet will travel much further than flat base because it flat base bullet creates more air drag

  26. rudedogii says:

    I dont think you under stand my comment. Do the light test with a High Flow filter like a K&N and then with a Fram paper filter. You will see a whole lot of light through a K&N and that is why they flow more air!

  27. What if you have trunk overs, like I have a 03 avalanche and out the tail gate down, will it still give be drag?

  28. TVsKevin says:

    If you can't see a backlight through your filter, like the sun, or a light bulb, it is clogged. A clean filter will allow a bright light to pass through.

  29. 7150285 says:

    so a sedan will be even more aerodynamic than a station wagon I am assuming. The best example is ballistic test of flat base and boat tail bullets, boat tail bullet will travel much further than flat base

  30. rudedogii says:

    This is what I have been telling people for so long. Thanks! Please do a video about Hi-Flow Air Filters. My thoughts are if you can see light through the filter dust can get through. Pros use them for performance but don't have to worry about dust and engine damage because the engine only has to last for one race. Guys like me need my engine to last for 100K+

  31. That black dust is likely burned oil from your exhaust. I'd check your oil level frequently to make sure you're not burning through it too fast. I have to add a half quart every 500 miles or so. But no, I wouldn't say that's why hatchbacks create a lot of drag. Designed right they can have equally low drag coefficients as other vehicles.

  32. Well, unfortunately some people buy trucks just to have a truck.

  33. Drive one way all of the time for a full tank, record distance on tank, and then repeat driving the other way and record distance.

  34. This guy is good. I wish I had him in Physics 101/02 when I was in college.

  35. Is accelerating quickly to the speed limit, say 60km/h, in second gear, and then changing to 5th, more or less economical than slowly increasing speed through the gears?

  36. No lol

  37. Mythbusters already did this.
    Tailgate up > Net = Bed Cover = Tailgate Removed > Tailgate Down.

    What I wonder is, will carrying a load in the bed interfere with that "force field of air" as you put it?

  38. 001GenLee says:

    What do you guys think about the tailgate net? I've had one on my ' 02 Ford Ranger since last summer and i thought i could tell a difference right off the bat, but not sure. The whole time, have i wasted more gas than saving by going with the net, versus tailgate up? If so, i may be putting the tailgate back on soon…

  39. shade460 says:

    I keep it up Because in my state, it is illegal to drive with it down. ;)

  40. Streamlines ,streamlines, streamlines… I loved fluids class.

  41. Nugenrules says:

    I agree, but your explaination seems a little biased. Tailgate up still creates a vortex behind the door, at least add that and say the turbulent force is smaller

  42. It may improve it slightly. Though in the city you've got more weight and never hit high speeds, so fuel economy will go down (very, very minor).

  43. Ray Cash says:

    What about a fiberglass clam shell tonneau cover on the bed? Does that detract from any tailgate up aerodynamic advantage?

  44. I actually did put model trucks (as part of a lab) in a wind tunnel while still in school, and the results were as I described above.

  45. maybach300c says:

    I think this is about (Skin Drag) V.S (Form Drag)
    The upper truck is Skin Drag > Form Drag.
    The bottom truck is Form Drag > Skin Drag.
    How do you think ? Am I right ?
    If you look at Corvette ZR1 or Ford GT-40, you would find the tail
    of these two sports car are more like the bottom truck.
    It is difficult to judge,so I think we should put the truck in the wind
    tunnel to test.

  46. Tom Nouri says:

    Tailgate down gains me about 1.8mpg over 200mile hwy driving intervals. I've measured it many times by topoff method and my mpg measurements don't lie. If ur presenting such a looped vortex in that there's enough resistance at base of the bed then the air should have no problem skimming over the top of it much of the same as tail up.

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