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Ryan
Dodge Dakota
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8/14/2005
15:19:43
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 Subject: MPG difference with the tailgate down?
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Does anyone know if there is a MPG difference if you ride with the tailgate down. I read once that the air flows a lot better and there is less drag when you ride the tailgate down. Thanks. Ryan.
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dodak05
Dodge Dakota
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8/14/2005
17:07:53
|  RE: MPG difference with the tailgate down?
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did my own test with my 3.7L + 4spd auto. Result was really too close to call and could have easily been the result of weather, traffic, etc. Over 3 tanksful of gas I didn't get more than 1 mpg change either way.
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kyle
Dodge Dakota
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8/14/2005
21:34:16
| RE: MPG difference with the tailgate down?
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I have always driven with my tailgate down or usually i take it off, i have never actually tested this theory but i have to beleive it makes some difference. i actually rigged up a way to open my tailgate half way to give it a spioler effect but again cant really say if it makes a difference.
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GB2000
GenIII
8/15/2005
00:35:11
| RE: MPG difference with the tailgate down?
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I think JFH is the one who's tested this...and he's an aeronautical engineer who works with this kind of stuff. If it was him I'm thinking of, I believe he said that it depends on the driving conditions...in town you'll get better gas mileage with the tailgate down, at higher speeds with the tailgate up (or better yet, with it angled partway open). Not positive though...search through old posts and see if you can find it...or if you're lucky, he'll post here about it.
Josh Blackshire - Owner, Ohio Dakotas .NET
Red 98 Dakota Sport - Check it out!
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Dan M
Dodge Dakota
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8/15/2005
06:03:17
| RE: MPG difference with the tailgate down?
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I recall reading somewhere on the web that someone did a test of this and found that with the tailgate down you get worse mpg. The Reason was that with it up, some air swirles in the bed creating a cushin and the rest of the air "bounces" off and flows over the tailgate. with the tailgate down, it creates a drag as it all flows out the back of the bed so it's not as aerodynamic. I'll have to search and see if I can find that article.
- Dan M
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WyomingPurple
Dodge Dakota
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8/15/2005
13:30:31
| RE: MPG difference with the tailgate down?
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From "Ask Yahoo": http://ask.yahoo.com/ask/20050427.html
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Joe M.
Dodge Dakota
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8/15/2005
14:02:30
|  RE: MPG difference with the tailgate down?
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ya who ??? LOL
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Joe M.
Dodge Dakota
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8/15/2005
14:14:55
|  RE: MPG difference with the tailgate down?
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#9 from http://ths.gardenweb.com/forums/load/saving/msg1018054326731.html
"9. Pickup truck drivers, don't lower the tailgate when driving on the highway. A GM study showed that this does not improve fuel economy, and can even make it worse. With the gate closed, air flows across the top of the bed and does not get "caught" by the tailgate. The airflow patterns are less efficient with the tailgate open or removed. Plus, running with the tailgate down can increase the likelihood and severity of a rear-end accident, since your tailgate will be extended behind your rear bumper."
there are some studies easily found on the net that show covering the bed does however improve fuel econo. (claims of 5 - 7%)
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bigdave
Dodge Dakota
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8/15/2005
14:32:29
| RE: MPG difference with the tailgate down?
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besides all that, its illegal in some states to drive with it down. It is here in Indiana.
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Billy Bob
Dodge Dakota
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8/15/2005
23:19:43
| RE: MPG difference with the tailgate down?
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how can driving with your tailgate down increase the likelihood of a rear-end collision??? because it extends beyond the bumper?? i wonder what that means for people who tow trailers beyond their truck bumpers?
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bigred
Dodge Dakota
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8/16/2005
02:07:54
| RE: MPG difference with the tailgate down?
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i put on a throttle body spacer on my 98 3.9L 4x4 and it has a camper shell on it now, and i'm getting around 18-20. big difference from before anyhow...laters
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uh big dave?
Dodge Dakota
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8/17/2005
18:45:33
| RE: MPG difference with the tailgate down?
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what about flat beds without a gate are they illegal? I dont think so big guy..
actually, if your load is not secured it is illegal, if the load is tied down to the bed it is not. that is why I traveled from chicago to rochester ny, with a 7 ft. couch in a 6.5 ft bed gate down but load secured, at least 6 cops saw it, one even gave us a speeding ticket in Indiana but NO ticket for the properly secured load on the Indiana Turnpike, actually he commended me for stapping in the load with ratchet straps. So in closing I would say that your theory is incorrect.
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Dan
Dodge Dakota
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12/13/2005
14:20:04
| RE: MPG difference with the tailgate down?
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Myth Busters (the tv show) proved the tailgate down theory as being FALSE! The mileage was actually worse with the tailgate down due to the lack of low pressure caused in the back of the truck with the gate down. With the gate up it keeps the air coming over the top of the truck from nose diving into the bad and causing drag.
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Dan
Dodge Dakota
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12/13/2005
14:21:37
| RE: MPG difference with the tailgate down?
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Myth Busters (the tv show) proved the tailgate down theory as being FALSE! The mileage was actually worse with the tailgate down due to the lack of low pressure caused in the back of the truck with the gate down. With the gate up it keeps the air coming over the top of the truck from nose diving into the bed and causing drag.
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intensedak39
*GenIII*
12/13/2005
19:51:21
| RE: MPG difference with the tailgate down?
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i saw that show.. pretty good testing they did.
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...
Dodge Dakota
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12/13/2005
22:44:16
| RE: MPG difference with the tailgate down?
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So would that mean having a cover on the bed does not help? Or would even make it worse like having the tailgate down?
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zzark
Gen II
12/13/2005
23:11:20
| RE: MPG difference with the tailgate down?
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Hey ...
Now you are asking a different question!
Go guys.
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prodak
Dodge Dakota
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12/13/2005
23:32:36
| RE: MPG difference with the tailgate down?
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The tailgate-down-increases-drag thing has been established for quite some time now. I'm sure the Mythbusters guys knew what to expect before they started (thus the name of the show, duh). The "bubble" of air (AKA locked vortex flow) with the tailgate up reduces the downwash behind the cab - tonneau cover does the same thing, only better since it's rigid.
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toolfan
GenIII
12/14/2005
20:43:59
|  RE: MPG difference with the tailgate down?
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i have drop the tail gate and the spare. with those to gone i notice that a tank of gas last me longer. i think instead of putting the tail gate down just take it off unless you need it!! don't recommend the spare but most my driving is around town and the spares on this trucks are heavy!!!
Sorry posted signature on 12/12 - 12/13/2005 that messed up FIREFOX screens! It worked ok in Internet Explorer. I'M SORRY!! Sincerely TOOLFAN
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02dakota
GenIII
12/15/2005
00:00:50
| RE: MPG difference with the tailgate down?
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I drove to work and back which is 40 miles round trip X 6days with the tailgate down,when i filled her up and checked the mileage i could'nt tell any difference. I just put the tailgate back up and thought hey it a 4 wheel drive truck and 20 mpg isnt bad.
Keith
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shdow
Dodge Dakota
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12/15/2005
04:20:00
| RE: MPG difference with the tailgate down?
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mythbusters did a segment on tailgate down
they said it's plausable and saves
and running a/c while driving didn't use enough extra gas worth mentioning
also with windows down not worth mentioning
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