The other day I went to SC and on the way back I decided to leave the tailgate down to see what mileage would be. I've seen the mileage test done on Mythbusters, but it was done with a short bed truck. Well the old dually got around 19 mpgs with me running between 70-75. Tailgate up, I only get 17-18 at best. I am thinking the longer bed allows the air to be caught by the tailgate instead of rolling over the air bubble created by the bed area of a shortbed truck. If you guys get a chance try it and report your mileage here vs tailgate up.

My dad has always told me that with it down you usually gain atleast about 1mpg. He has done this with many different trucks all were long beds. I have also noticed 1mpg gain out of my 99 454 crew cad 4x4 dually and a 3/4 to 4x4 6.0.

on the same premis....I noticed at least 1mpg with my tonnoue cover on..

I used to drive with it down on my dodge dually.I left it down for a few thousand miles then i noticed that the tailgate was beat all to pieces rock chips ect.I dont think the fuel savings justified what it cost me to have my tailgate repainted 450.00

Welcome to planet earth:)

http://www.youtube.com/watch?v=r3aqHbD-O9E

Welcome to planet earth:)

http://www.youtube.com/watch?v=r3aqHbD-O9E

Notice they used a shortbed truck. The premise of my post is that the longer bed of the dually allows the air to be caught by the tailgate instead of just rolling over like it does in a shortbed. I got better mileage than I ever have by putting the tailgate down. i just wanted to see if others with longbed duallys have had the same experience. Do you have a dually and have you tried it?

I tried it driving from Wisconsin to Florida and my DIC went from 18 to 16 half way. I put the gate back up and it went back to 18. This was b4 the edge.

I got significantly better mileage with the tailgate down because all the crap in my bed fell out.

I have always had at least a mpg difference and have always had long-beds.

You (or at least I) can feel the turbulance with it up vs. down.

I got significantly better mileage with the tailgate down because all the crap in my bed fell out.

I would be arrested for an unsecured load.

The problem is, there is no controlled way to test the theory because of uncontrollable variables. Hills, changes in wind, trucks that are tuned different to start with, traffic, temperature, fuel quality, speed, and many others will change every time you drive the truck.

I could also argue that when you have your tailgate down, you are expecting to get better mileage, so you accelerate more gradually, coast more, drive slower, etc.

The best thing that I have done for fuel mileage is slow down. I have not noticed a measurable difference with anything else. Tuner, Bed Cover, Synthetic lubricants, tires, exhaust, air filter, etc have verly little effect by themselves, but collectively, may be good for a mile or so per gallon.

Slowing down from 75 to 65 MPH raises my mileage from around 17 to around 19.

Notice they used a shortbed truck. The premise of my post is that the longer bed of the dually allows the air to be caught by the tailgate instead of just rolling over like it does in a shortbed. I got better mileage than I ever have by putting the tailgate down. i just wanted to see if others with longbed duallys have had the same experience. Do you have a dually and have you tried it?
tell you what, I will give this a try this week and report back to you on my findings.

tell you what, I will give this a try this week and report back to you on my findings.

ty, I haven't had a chance to drive much here lately, but from before tailgat down seemed better driving all Interstate at the same speeds.

Years ago I had a '72 Chevy SRW with an 8 foot bed. I drove with the tailgate down and noticed better gas mileage. However, with the tailgate down, the sides of the bed are unsupported and eventually rattled loose and came apart driving on a lot of dirt roads. My brother and I ended up making an angle iron frame to replace the tailgate and put wire mesh across it. I still got better gas mileage than with the tailgate up, and the sides were supported so they didn't flop around. I don't drive with my tailgate down with my '07 for that reason, although I'm sure I would get better mileage.

Shark

I ran a 60 mile trip today. 120 total
way up I got 21.5 empty with tailgate up.
back I got 19.7 tailgate down. ran the same speed both directions and had no traffic.
this was not measured at the pump, it was according to the DIC. but, for some reason my DIC is usually within a tenth or two of being correct.

next time I run that trip I am going to have the tailgate down on the way up and up on the way back to see if the difference is because of the tailgate, or the lay of the road.

I ran a 60 mile trip today. 120 total
way up I got 21.5 empty with tailgate up.
back I got 19.7 tailgate down. ran the same speed both directions and had no traffic.
this was not measured at the pump, it was according to the DIC. but, for some reason my DIC is usually within a tenth or two of being correct.

next time I run that trip I am going to have the tailgate down on the way up and up on the way back to see if the difference is because of the tailgate, or the lay of the road.

Wind, Temperature, etc could change mileage. 19-22 is pretty impressive for a 7700 lb dually pickup. I strive for 20, but usually end up falling slightly short at about 19.5

How you guys get the mileage you report is beyond me-

Unloaded with no one but me in the truck I might get 14 mpg- and that is a big maybe. My 2002 Duramax was about the same.

19-21 mpg at 65 or 75? Wow!

How much brake dust is built up on your front rims will tell alot!

I coast very often to a stop. I just replaced my brakes at 250,000. I haul farm drainage equipment all the time and it does not have any brakes on the equipment. The stuff ways about 11,000 Lbs.

Empty at no faster than 68 MPH 18-20 MPG, every bit above that drops the mileage. at 72 MPH I get about 16.5. This was all manually checked, I don't have the trip indicator in my DIC as I don't have the buttons on my wheel. I have been running a scan guage in my truck for almost 200,000 miles. It will tell you when you are maxing or wasting fuel if you are running against a strong head wind, instant feed back.

19 is strictly highway driving, and empty. I coast a lot when coming to a stop. Brakes convert forward energy to heat. Keep my speed at about 70MPH or less, try not to put my foot in it to hear the pipes (and tires), and try to get up to speed quickly to get to od gear without mashing the go peddle. If I get above 70mph, the mileage drops off very quickly. My wife thinks I drive like a grandpa when I'm trying to get good mileage.

I have changed my transmission, engine oil, and differential fluids to synthetic, running 235/85/16 tires, and a tuner, and installed a cover on the bed. The engine oil seemed to make the most measurable difference, aside from speed.

Average between highway, city, and some towing for about the last two years, I am getting about 16.5, towing 13, and town only around 16.

How you guys get the mileage you report is beyond me-

Unloaded with no one but me in the truck I might get 14 mpg- and that is a big maybe. My 2002 Duramax was about the same.

19-21 mpg at 65 or 75? Wow!

my hot rod dually gets 18-19! take the emission crap off!

I take off slow, I dont cruise too much over 65 and I honestly average over 18 driving back and forth to work on the Washington Beltway.

Well i went to Nashville yesterday and as soon as i hit open interstate, I reset the DIC fuel mileage. It is within a couple of tenths of hand calculated every time. Going up tailgate down, 17.8 at 70-75. Coming back 17.8 with tailgate up. I think there was a slight headwind coming back, but you also get better mileage coming back Monteagle towards Chattanoooga because you don't have touch the go pedal for around 5 miles, so push.

The best mpg I get is going from 4000 ft down to sea level on the DIC is 20.1. On the return trip I get 18.0. Truck is empty and going 60 mph. It is about 100 miles each way.
I have a vented 5th wheel gate.
I will someday try this trip with the stock gate. I use a edge tuner set on level 1

Good thread. Was considering taking the tailgate off, it's pretty beat up from the previous owner towing with a fifth wheel and banging into it with the front of the trailer. My neighbor has a vented fifth wheel tailgate on both of his trucks. I've heard about the bed rails getting weak and cracking because of no gate being in place, but since I don't off road, I believe I'll be OK. I've also considered getting a mesh air gate for hauling stuff around.
In the Mythbusters episode, I also noticed they didn't try removing the gate before adding the air gate. The weight of the gate could have skeewed the results too.

Up date: Took my tailgate off with a 1/4 tank left, got just under 16MPG. 80% highway/20% city driving. Got around 14MPG this past week with it off. Going to go another week with it off, if it stays around 14MPG, I'll be putting it back on or getting an air gate.

I keep my tailgate up for two reasons; there's always something in the bed that I don't want to lose and if a Mexican with no insurance rearends me, I'd rather catch his honda on my trailer hitch than my tailgate..........