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Interior & ExteriorDiscussions about the interior, and exterior of your vehicle.
This is a discussion thread titled "Mileage increase with tailgate off", within the Interior & Exterior forum, part of the Technical & Vehicle Assistance Forums category.
Your correct. To eliminate as much variation as possible you would need to use the same pump and nozzle during testing, and even then there will certainly be variation in the filling cutoff. You can get a fairly decent approximation, but I would think that the error involved would be about +/-0.1g or so. Just a guess
Just how precise do you want to be?
Just doing a quicky sample run in excel, doing 300 miles and doing a range of values from 22-23 gallons in 0.1 gal increments produces a variance of roughly 0.05 MPG. So, depending on how far off you figure your gas pump shuts off each time, I don't think it's gonna matter much. Add in that most gas pumps are required and tested by states to be within about 5/10ths of a percent delivered and reported for additional variance. It varies depending on which state but it seems to average around 5/10ths of a percent. If you wanted to be even more crazy about it, you'd need to factor in the change in density given the temperature.
If you're worried about being that precise, you need help....
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Genthar
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Hey ED---Where was this great deal back in August when we had are group buy? Any chance the could retroactive back to then? LARRY
If I were you, driving off-road with the tailgate off, I would seriously consider getting some sort of brace bar, to go from one side the the truck to the other (in place of the tailgate).
I saw a pick-up where they guy always had his tailgate off, and he had crack where the bed floor met the side of the bed.
Last year (I think it was last year) Truck trend did a big test on that, and proved that tailgate down decreased your aerodynamics. Also, myth busters did a wind tunnel test on it and again proved that tailgate down made it worse. With the tailgate up, it creates a vortex in the bed, causing a continous circulation of air. If you put a piece of paper in the bed of your truck, take notice that it blows to the front of the bed. The same air will constantly circulate around the bed causing the air coming over the roof to just pass by over the top of the bed, again showing why the tailgate gets so dusty. As to toneau covers, they do help, but is the cost of a cover worth .5 mpg?
The boys in Detroit dissmissed the myth years back, can you believe they actually figured that one out! To bad Craftsman Truck Nascar Guys can't let their tailgates down!!
Mythbusters revisited this myth and reconfirmed that the tailgate down does decrease mpg. They also tested with a hard tonneau and a Gator Net. In their test the tonneau also gave worse gas milage, but the Gator Net improved it. Go figure.
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I didn't read all of the responses. I recently watched an episode of myth busters on this particular subject. Final outcome was that you reduce mileage by at least 5% when tailagate is removed.
Cause: removing tailgate creates a vortex vacuum off the back of the truck. Kindof like dragging a parachute behind you.
Tailgate on: air vortex circulates in the bed trapped by the gate. air then passes over the air bubble and over the gate.
Bed Cover: Only increase in mileage. About 3-5%. Like a foil no turbulance air passes smoothly over the bed and off the back of the truck.
it's like...echinacea tea...or "healing crystals"...or the healing power of magnets...or snake oil...or megavitamin therapy...
"well, it works for me, even if it doesn't work for you."
not so, says science . it's too bad people are still willing to accept the old "works for me" explanation, when scientific evidence shows that in most cases, it doesn't "work for them" any more than it does for anyone else. yup...doesnt work, the idea of letting the tailgate down for better mileage is just plain wrong. not wrong except for one guy somewhere, but incorrect, period.
I used to drive around with my tailgate down thinking it reduced air resistance until I also saw Mythbusters feature this issue. Those guys have the coolest job!
__________________ 2002 Tundra AC 4x4 Off Road Package - Revtek coil lift with Wheeler's 1.5" AAL. Superlift Truspeed Recalibration unit. Flomaster dual exhaust. Husky floor liners. Hellwig anti sway bar. Xmas Gift 2006 - 3" Perf. Accessories body lift and Gap guards - Installed 1/6/07! New tires in March 2007 - BFG AT 30570r16 on MT Classic IIs. Total Chaos steering bushing kit. Front swaybar bushing kit from Wheelers Offroad. Stubbie 21" antenna. Underdrive pulley installed with NAPA belt. Timing chain replacement and brake job are next!
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Any chance the could retroactive back to then? 
LARRY
Re: Mileage increase with tailgate off
. it's too bad people are still willing to accept the old "works for me" explanation, when scientific evidence shows that in most cases, it doesn't "work for them" any more than it does for anyone else. yup...doesnt work, the idea of letting the tailgate down for better mileage is just plain wrong. not wrong except for one guy somewhere, but incorrect, period.
2002 Tundra AC 4x4 Off Road Package - Revtek coil lift with Wheeler's 1.5" AAL. Superlift Truspeed Recalibration unit. Flomaster dual exhaust. Husky floor liners. Hellwig anti sway bar. Xmas Gift 2006 - 3" Perf. Accessories body lift and Gap guards - Installed 1/6/07! New tires in March 2007 - BFG AT 30570r16 on MT Classic IIs. Total Chaos steering bushing kit. Front swaybar bushing kit from Wheelers Offroad. Stubbie 21" antenna. Underdrive pulley installed with NAPA belt. Timing chain replacement and brake job are next!
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