Home Forums Hunting & Shooting Hunter's Campfire Tailgate up or down. Which is better?

GM says it ran wind tunnel tests that show that up gets you better mileage.

Tailgate up or down? GMC solves age-old pickup truck mystery

Published May 20, 2013

FoxNews.com

It�s an age old conundrum among pickup truck owners: tailgate up or down?

We�re talking aerodynamics and fuel economy here, but without personal access to wind tunnels, the evidence most owners have to support their position is anecdotal, at best.

Many split the difference between form and functionality and replace the tailgate with an open net that lets the air through, but not their cargo.

GMC says that�s a bad idea.

While testing its all-new 2014 Sierra pickup truck, the automaker determined, unequivocally, that it cuts through the air more smoothly with the tailgate closed, and optimized its design to increase the effect.

Perhaps not surprisingly, it also found that using a net is actually worse than having no tailgate at all.

The company says this likely holds true for all of its pickups, not just the new model, but there are a few aftermarket add-ons that can effectively improve your MPG. Tonneau covers for the bed help clean up the air flowing over it, and properly-designed running boards can help as well.

Along with the attention spent on the rear of the trucks, the front of the new Sierra has been designed to direct the airflow out and around its tires and down to the ground to clear the nooks and crannies of its underbody.

It may still look like a box on wheels to you, but the air sees things slightly differently.

Myth Busters did a episode about a year ago without a wind tunnel.
They used two identical pick-ups, drained the fuel tanks, then put an equal amount of measured gasoline in each truck.
They put them on a track to see which ran out of fuel first. The truck with the tailgate up went quite a few more miles before it ran out of gasoline.
And they didn't need to run a million dollar wind tunnel test like GM- AK Governtment Frickin Motors... Screw GM! I'd trust Myth Busters over them any day

Mythbusters did a test several years ago using 2 identical pickups, one driven tailgate up and the other tailgate down, and concluded the same thing.

Mythbusters has some flaws in their testing, though. They did the same thing with 2 identical Suburbans to see if they got better mileage with or without the A/C running. There were 2 major flaws in their test.
A. they only ran at 45 mph around a track. Wind resistance grows exponentially at higher speeds.
B. They didn't switch cars and run it again. Even though the cars were identical, they could very well get considerably different mileage.

Many of their tests are fun to watch and somewhat educational, but they'll seldom stand the scientific test.

How can anyone in good conscience drive around with their tailgate down anyway? What if some of your valuable stuff or your kids or your dog falls out?

They use nets, which GM claims to be worst of all. They didn't say why but I'd guess that the flapping fabric catches a lot of air.

With my '92 reg cab, long box chevy I got better mileage with the tailgate down. I don't remember the difference, and it wasn't much, but it was there. I can't speak to any other body style though.

Up forces air flow over the top of the bed, putting less drag on the whole vehicle.
Down apperantly lets it produce friction over the bed.
Net, it seems to be worse. Air flows over the bed surface and a drag on the net itself.
Hard covers seem to do a little bit better than tailgate up, just a little more slick without the hole in the middle.

Each vehicle has a difference shape (BC) and as we know BC can vary a bit by speed.

Best advice is to try it with your own vehicle and see. What's the worst that can happen?

Blanket statements about tailgate up or down can't be made.

A 2013 GMC doing 70 will go through the air much different than a 1999 Ford at 60 etc.

I know, hand calculated over several tanks, that I got better mileage out of my Toyota with the gate down.

Believe it or not, its illegal to run with your tailgate down in Minnysoda. Reason is that an unlocked gate could bounce out of its pivot points and tear the cables off.
Yeah its far fetched but I responded once to aid an adjacent jurisdiction where a tailgate flew up and hit an oncoming van.
The gate went into the windshield and killed a teenage boy in the passenger seat. Strapped in, there was nothing he could do but die when it crushed his skull.
So if you want, take it off and put on a cargo net.

And, given all of the variables, I would bet that what works best for any given person in any given pickup is exactly what that person wants to work the best.

When I first got my 98 Dodge Cummins, I went from Colo Sprgs to Columbia MO. About 700 miles. 1/2 with the tail gate up , 1/2 with it down. No difference in mileage at a all. I use a metal air gate now.

Running with the tail gate down can sure mess it up on a gravel road with the rocks bouncing up. Some think they won't bounce up that far, but I have seen two or three that were pocked marked

or if it is raining, your wife. All good rednecks put the dog up in the cab when it rains, and the wife in the back.

Lower looks Cooler ...

Old news. I can't remember which magazine, but one of the truck or 4X4 magazines did the same test back in the 70's. I remember a similar test by Outdoor Life in the 80's or 90's and two or 3 episodes of Myth Busters. Results have always been mixed. Some show something like .1 mpg better with it up, some show .1 mpg better with it down.

At best you'll never save enough money on fuel in a lifetime to pay for the potential damage that could be caused by driving with it down.

I was driving up a dirt road to a public shooting range once when I looked back and noticed my tailgate had popped open and three rifles had fallen out. A half mile back down the road I met a Jeep. We stopped, he asked if I was missing something, and luckily I got all three guns back.

Screw fuel mileage; guns are expensive.

All three rifles were still zeroed.

The only ticket I ever received while living in Colorado was for driving on I-25 with my tailgate down. Don't remember if it was illegal just on the interstate, or everywhere.

There are a couple of pickups here in our little community without tailgates--they fell off while the owners were running with them down and are so banged up that they will no longer close. On one truck, one of the cables held, and the tailgate did quite a dance before the owner got it stopped!

On many newer trucks replacement is expensive and come with locks that only work when closed. My brothers neighbor had the gate stolen off his F-250 when he left it down. Replacement cost was around $3000. This was one with the built in step and back-up camera.

Human smugglers prefer the tailgate up so you can fit more illegals in the bed.