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fiction!! mythbusters tested this theory, and it actually turns out that lowering your tailgate while driving decreases gas mileage, because with the tailgate closed,it creates a vortex that air runs right over, with it open,it somehow causes drag!! it was actually a pretty cool test.

They did a revisit episode, and actually the best mileage they got was with a tailgate net.
 

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Lowering your tailgate while you drive will improve your MPG?

Fact or fiction?

Thanks.
Definite fiction.

This is a quote from “Fuel Advantage - Spring 2007” (A trade journal for fleet managers)

Read The Full Article: http://www.fuelpub.com/print/Fuel-Advantage/Slipping-Through/1$26


Slipping Through
Is aerodynamic design the final frontier in improving vehicle fuel efficiency?


"If you ask Kevin Cooper about vehicle aerodynamics, the first thing he’ll want to talk about is tailgates. The consultant and former vehicle aerodynamics researcher for National Resources Canada (NRC) has been trying to get the message out for years that if drivers leave the tailgate of a pickup truck down, they will actually get worse fuel economy than if they kept it up and latched."
 

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Fiction...absoultely no increase when I added the tonneau cover.
 

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The net effect of camper shell is negative between added weight (negative) and possibly better aerodynamic (positive).
 

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+1

I lwent from just over 20mpg to just over/under 19mpg when I added my Leer cap.

Tacoma 2x cab, 4x4 6 speed. sr5.

no idea how much the fiberglass cap weighs.
I had exactly the same results with a Leer canopy installed on my Ford Ranger. It dropped about 1 mpg.
 

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99.9% of the people would say its fiction. But if Myth Busters and professionals say it is, then I have no chance in fighting. A guy tested this with his F-150 with a scan guage II. He did 2 trips both the same distance and speed. Turned out the trip with the tailgate down improved with +0.1 mpg. Here's a link to it. And heres the opposer. Also, when I race at the track, I can improve my time by a whole .2 secs with the tailgate down.
 

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I have 40k on my 2005 Tacoma and I lower the tailgate about half the time when cruising the highway and I definitely see a 1-2mpg improvement with the gate down.
 

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Mythbusters as mentioned above.....posibbly both crap studies as they said themselves with non-reproducible results 1st - tailgate up was better, 2nd - tailgate net was better. Both create a box full of swirling air which creates an airsweep similar to a 4 runner or SUV body style. Gate down = little worse.

I've got an axxess tonneau and put plenty of miles on driving to school & back and I don't notice much difference if any (over 500km with both to a tank).
 

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You got >20mpg with a DC V6 manual 4x4? Is that highway only?
My truck is an '07 auto 4x4 Sport TRD access cab with a net tailgate and I check my gas mileage after every fillup and never get less than 20mpg or more than 21mpg unless I've been towing my 3500# motorboat. Most of my driving is not highway OR city driving and instead is mostly rural driving at speeds between 30 and 60 mph.

The reason I installed a net tailgate is not to get better mileage though, it's so I can see the tongue of my boat trailer so I don't back into it and scratch my bumper. :eek:

Since first seeing this thread, I've been paying more attention to my net tailgate while driving and it doesn't seem to be pushed either forward or backwards when I'm cruising down the highway at 70mph. If there were any forward or aft forces being exerted on the netting that might be strong enough to significantly alter the overall drag of the vehicle and thus affect the gas mileage, I would expect to see the netting bending forward or sagging aft while underway.
 

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[no_ads]This was tested by a college back east both in a wind tunnel and in practical application long before Mythbusters did it but the results were the same. Tailgate down yields the WORST mileage, Tailgate up was better, and a tonneau cover with tailgate up is the best by a wide margin in a wind tunnel but is slightly offset by the added weight in real world driving. With the tonneau was still the clear winner.

Adding a cap makes the truck more aerodynamic right up to the point the wind gets to the back of the cap, then the added turbulence of the larger flat rear area actually causes more drag than with no cap.

Phil :tu:[/no_ads]
 

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Interesting on the MPG comments. I installed a LEER tonneau 2 years ago ('05 DC 4x4 Lng Bed) and didn't notice a difference. I do a lot of rural and hilly highway driving and see consistent results. Locally I always get 18.5 (and that's doing 75 on the freeway in the mountains so there's a lot of climbing involved). On long trips I see 22 consistently.

Just what the sticker said I should get.
 
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