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.

I had one fall off on a ford, it wouldn't stay latched and popped off then it was so bent the pivot points barely held it in

Only for larger illegals....with the smaller ones you can get another three rows of them sitting on the tailgate, more profit.

Seriously, who gives a $hit? We all, or most of us anyway drive full size gas hogs, myself included. I'm not small and I don't like cramming my wide a$$ into a mid-size. I like full size trucks/SUV's! I am perfectly willing to pay more at the pump for comfort and functionality. Maybe that's just me.

Mike

Bingo. I didn't buy a 3/4 ton 4x4 diesel for fuel economy.

Here's the best stat...keep it up...sooner or later you will back into something with the tailgate down and ruin it. Ever notice how many truck tailgates you see out there with nice round pole dents in em'

My wife refuses to ride anywhere in my truck. My dog, unlike my brothers' sissy-ass golden retrievers, never gets to ride in the cab.

We have a Dodge 4 door long bed. My wife LOVES it. She doesn't really like to drive it but she sure likes the comfort and size of it.

With the tail gate down, my truck accelerates faster and get to speed faster.

I believe its been proved the most economical is to have a tonneau cover fitted over the bed.....

UP.

Gunner

no chit, im just over 6 foot and i hate most cars......the lil thing we had to rent when going to Kates graduation last week really sucked, not made for guys like me to get in and out of and i didnt even have a winter coat on....i like my truck.....

I seem to recall on that myth busters episode they found that no tailgate at all was the best gas mileage.

Heh.
Same here.

I take my longbow when vehicle shopping.

We will both fit comfortably.
And that is our final answer.

throw in a pair of worthless knees and it makes it even worse.....only had the car for a day but was very happy to drop the SOB back of at Hertz....

Why do I get a big smile reading your posts on this thread?

cause your easily ammused.........that or you picture me taking a face plant in the back of that truck......its prolly one or the other...

It wasn't funny until I was 100% sure you were ok.

My damned beer cans roll out with the tailgate down.

thats far from the worse spill ive taken cause of my damn knees....the entertaining ones are when they hyper-extend unexpectedly.....those usually involve inventing a bunch of new cursing combinations and me crawling around on the ground...

Darla thought i had lost my mind the first time it happened cause i was just stepping up into the truck and when i put my weight on the left leg it popped backwards....had to grab on to the steering wheel to keep from hitting the ground and then pull myself up to get it to pop back into place...Darla thought i had suddenly developed Tourettes....

I can't tell any difference on my truck. Oh, wait, tailgate down delivers me from the clutches of the overhead tollway camera, I'm savin' $$$$

Personal experience tells me that it is a lot cheaper to run with the tailgate up, even if the rig delivers less fuel mileage that way.

The tailgate up locks the two side of the bed together and stabilizes them. Leaving the tailgate down allows the sides of the bed to vibrate and flex independently, which will eventually necessitate the purchase of an entire new bed.

At least that is what happened to two pickups I have owned.

While visiting Greenvile, SC years ago a huge buck in the back of a PU with no gate fell out onto the road ahead of us.

We followed the truck to a diner and returned the buck to the hunter.

The look on his face was priceless.

Denny.

Now THAT I didn't know... Thanks for the info - although I don't run with it down anyway.. Still, ------


Ok, now what if you're just coming from the local lumber yard with some 10' 2X4s in the back, laid flat.. Tailgate's down, but covered with the wood.. Illegal??

I would like to hear everyone's opinion on Tonneau covers. Do they increase or decrease mileage? I would never run with a tailgate down unless I had something longer then bed length back there that weighed a bunch.

That part, I don't know.. But I've had 'em on the last two trucks I owned and wouldn't go w/o one..

This one I ordered with the truck:

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Keeps the bed clean and dirt/crap off the Reese 5er hitch underneath it..

If you read the article in the OP, GM said that a tonneau works very well to increase mileage.

Get a vehicle built for the job.

Tailgate up and tonneau cover on is def. the way to go.

LMAO.. Oh, Lordy, that reminds me.. Not to get off topic, but at one time when I was doing a bit of truck farming I bought some crops from other farmers that I couldn't grow here..especially muskmelons..

Old Harry Shindledecker in Cannon Falls, MN grew the BEST melons, and I would often buy his entire crop. One day in August I showed up with my (then) Ford Pinto wagon and he had about 15+ bushels of melons.. Hadda load 'em in loose in order to take 'em all home.. I had melons EVERYWHERE - only enough room to drive and I figured there was about 1200# in that car.. I think it looked somewhat like that pic above...

Gotta agree with Redneck (that should ruin his day )

I use a tonneau cover as well. They are hard to beat for versatility.

This is what happens when you let your son-in-law and daughter borrow your truck to move and they leave the gate down. The cost to repair this would buy me enough gas to drive 3,000 miles.



Yea, but they don't say by how much. This stuff has been beat to death. Since the oil embargo of the 1970's guys have been searching for a way to get better fuel mileage from their trucks. Tailgate up, down, with or without a tonneau cover or shell the difference is usually no more than about .1 or .2 MPG. I'd save less than 50 gallons of gas after 100,000 miles if I increased my fuel mileage by .2 mpg. I'd have to put 500,000 miles on my truck to save enough on gas to pay for the tailgate repair.

Wanna know how to get better fuel mileage. SLOW DOWN. In October 2010 I drove to Colorado to hunt with my BIL. We were working in a very narrow time frame to drive 1700 miles, hunt, and drive 1700 miles to get him back for work. We drove 80-85 mph straight through going and coming. My Tacoma averaged 17-18 mpg. I made essentilly the same trip 6 months later for a summer camping trip with my wife. We were in no hurry and drove 65-70 mph and averaged 20-21 mpg on the trip.

Tailgate up should make the rear of the truck more obvious to the driver behind you who's on the phone, texting, gaming, fussing at the kids, etc.. Tailgate up also gives the same person a little more distance to get their vehicle stopped before it hits some part of yours.

drive with your gate down and u will arrive at your destination with out your stuff.

Traveling light will also lead to better gas mileage