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Dak_Yoda
Dodge Dakota
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2/04/2002
16:28:40
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 Subject: Does tonneau = better milage?
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Will adding a tonneau cover actually increase gas milage? Does a tonneau cover actually pose any aerodynamic advantage? Isn't the whole bed area of your truck just a big vacuum pocket at speed on the highway anyway? I'm thinking it is, infact that the air just travels around the nose of the truck and over and around the curves of the cab, then when it gets to the back of the cab it seperates from the truck and doesnt' actually go into the bed and cause drag. Can anyone offer any insight to this?
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scat pack
GenIII
2/04/2002
16:53:43
| RE: Does tonneau = better milage?
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A turbulent boundary layer of air forms there. dropping tailgate distubs this and makes is worse,adding a tonneau smoothes it out for less drag.
2K RC 4.7 4x4
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Dave Mitchell
Dodge Dakota
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2/04/2002
17:17:24
| RE: Does tonneau = better milage?
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My gas mileage increase when I removed the tailgate from the truck. But I have no tonneau cover, either.
I went from 21MPG to 23.5MPG...
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alex
Dodge Dakota
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2/04/2002
17:27:07
| RE: Does tonneau = better milage?
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The bed creates a huge suction area behind the cab and the tailgate compounds the problem even worse. The tonneau cover got my 4.7L 3.55-geared truck 1.5 more mpg on the highway. Definitely worth the $250 (basic soft-cover).
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Dodgedogjb
Dodge Dakota
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2/05/2002
02:29:21
| RE: Does tonneau = better milage?
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I have a Pace Edwards Tanneau cover and I never really saw much difference in gas milleage. I never got the chance to take a long trip on the freeway though before I got it on and I think a long trip on the freeway is the only real way to tell. Around town and short trips at freeway speeds have so many different start and stops its hard to compare tank to tank. The biggest thing I did notice is that the truck seems to be less affected by wind gusts from Semi's and nasty weather. The added security is worth it alone regardless of better gas milleage. Not to mention keeping things dry and from blowing away.
Joel
99 5.2L 4X4 CC
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Bill
Dodge Dakota
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2/05/2002
07:20:18
| RE: Does tonneau = better milage?
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I got an ARE fiberglass tonneau on my 3.9L CC 4x4 last November. Like Joel, I noticed hardly any difference in my gas mileage. I still only get around 16-17 on the highway. But I don't regret getting one. I can finally keep stuff back there and not worry about it blowing around and getting wet. Well worth the money. It is also really easy to remove (just take off 4 clamps) so I can take it off when I need more height. ARE is a great cover! Pics of it on my website.
Bill
http://members.aol.com/btaylor04/BTruck.html
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Todd Bouton
Dodge Dakota
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2/05/2002
08:35:07
|  RE: Does tonneau = better milage?
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What would a camper type shell, like the 'Leer' do? One thats the same height as the cab, no higher up area near the back?
Any experiences with these?
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alex
Dodge Dakota
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2/05/2002
10:27:31
| RE: Does tonneau = better milage?
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That moves the suction out of the bed and then bak behind the camper/bed area. Ever seen a Peterbuilt driving on the interstate without a trailer in the rain? There's a huge cloud of mist coming off the tires and then it swirls up and around and is mostly just suspended behind the cab. That's the giant suction I am talking about. Pick-up trucks are not aerodynamic in any way, but the tonneau cover is probably the most "bang for the buck" when it comes to aerodynamics (and therefore gas mileage).
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Dan Gruber
GenIII
2/05/2002
12:11:37
| RE: Does tonneau = better milage?
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Check this website. Real world results will vary, but this will give you an indication of what the aerodynamics of various setups are.
http://mars.acnet.wnec.edu/~ehaffner/did.htm
Dan
2000 CC SLT 4.7 4X4 Auto 3.55 LSD
3 inch Performance Accesories lift & 32 inch BFG MT KM's
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Me
Dodge Dakota
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2/05/2002
13:32:16
| RE: Does tonneau = better milage?
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Since I couldn't afford a tonneau cover I bought a tail gate net. I gained 1-1/2 to 2 mpg with a $22.95 investment. Paid for itself very quickly.
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Dak_Yoda
Dodge Dakota
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2/05/2002
13:47:02
| RE: Does tonneau = better milage?
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hey Me, if you read the stuff from the link right above your post you'd know that a tailgate net causes drag, and a tonneau cover is the best for decreasing drag, so look at that link, its quite good, and thanks to Dan Gruber, that link actually answered my question with real numbers and excellent info.
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Me
Dodge Dakota
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2/05/2002
16:34:53
| RE: Does tonneau = better milage?
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Ok the pictures are nice & I believe what is being said. Maybe it is the weight loss from the tailgate removal. Wouldn't a lighter truck get better mileage in most cases.? Say what you want but I check mileage at every fill up. Mine did go up. And it didn't cost me over $150.00 to see a minor increase.
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scat pack
GenIII
2/05/2002
17:27:53
| RE: Does tonneau = better milage?
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I stand corrected. Excellent info on that website, I confused dropped tailgate with removed tailgate ! Maybe your milage has gone up because you're being more concientious about driving for higher milage ?
2K RC 4.7 4x4
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boomndakota
Dodge Dakota
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2/06/2002
09:31:59
| RE: Does tonneau = better milage?
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Todd,I have a Leer truck cap on my RT,the more expensive model with the flush style windows.I cant say much for the fuel economy,as I didnt really compare,I would have to guess about the same.The one thing I can tell you,is that the cap adds alot more weight than even a fiberglass tonneau would,do to the glass,perhaps a cap without windows,or even the non flush style would have less glass.The weight is most noticeable while turning,it definately feels much more topheavy.It also seems to lift the front end up slightly,and most definately is noticeable taking off,where the rear end dips far more than without the cap.Its a nice cap,but I would suggest the tonneau unless you require the added space.In fact if you are dead set on the truck cap,and your truck is black,I'll give you a good deal on the cap!....better off with the tonneau!
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Dak_Yoda
Dodge Dakota
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2/06/2002
09:43:51
| RE: Does tonneau = better milage?
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yeah, caps are enormously heavy and not for any kind of performance whatsoever, gasmilage, aero, or otherwise
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