Has anyone ever done a careful test of whether a pickup gets better mileage with the tailgate up or with it down? Assuming no cap of course. I seems like it would be better with the tailgate down, but I've never actually checked the mileage one way and then the other.
Danny, you'll get lot's of opinions on this and very few facts. I wanted to collect facts during a college fluid dynamics class but the instructor wouldn't let me. I was going to run a model in a wind tunnel to compare. Apparently it had been done before with no difference so he talked me into some other test (which I've long forgotten). I have heard that a toneau cover will help some. You'll get the most mileage improvement just by being conservative with your right foot [img]/forums/images/icons/smile.gif[/img]
Rob
I don't know enough to believe this or not - maybe someone else can chime in...
A lot of people around here say that leaving the gate open or removing it altogether will eventually damage the box as rigidity is reduced.
I'm not quite sure WHERE I saw it, but I remember that I was a bit surprised reading it ... it was a study on this exact subject ... reviewing the mesh tailgate replacements and the like .. including tonneau covers ... and the reported variation was negligible. AIR, the article used some wind tunnel/smoke tests and reported that the closed gate seemed to make it act as if it was "covered" ... in other words the air in the box made the box "full".
I'll see if I can figure out where I read that review.
pete
it's a shame that common sense isn't
You're right wingnut no difference at all. [img]/forums/images/icons/wink.gif[/img]
Wingnut,
I read of the same study that the airflow in the bed of the
truck creates a bubble which cuts down on drag.
I did a test a few years ago with my tailgate up/down.
I had to drive to GA from NC and back in one day. Five hours
down and five back. I drove down with the tailgate in one
position and changed its position of the drive back.
The bottom line was that the milage was almost the same. It
was off by something like .1 MPG and that was on the drive
down. When I got to GA I had to drive around looking for an
address so I wasted some fuel figuring out where I was
supposed to go. On the trip back I did not have that problem.
[img]/forums/images/icons/grin.gif[/img]
So it was the same truck, different fuel, same weather and
same roads, and the milage was the same.
Later,
Dan McCarty
yap up in deed creates a circular bubble of counter rotating air in truck bed area lowering the amoung of air drafting back and creating a low pressure area thus slowing the truck when the low pressure area isn't there no increase in drag..
so leave it up and in place..
Casual tests (anecdotal, non-scientific) and uninformed surmizes are interesting but mostly useless.
First, this, my kindred spirit: Sorry you let your proff squelch your testing. I wanted to pursue active noise cancellalltion in 1968-9 but acoustics proff laughed me out of his office.
Auto makers do extensive testing these recent decades in attempt to keep the "fleet" average fuel consumption in check. Some of us really got into this a few years back and could find no evidence that any production pickup sold in America got beter mileage with the tailgate down or removed. Ditto for the cargo nets and louvered gates. Previous poster hit the nail right on the head! Aerodynamics of pickup with empty bed, gate up is almost identical to same unit with tonneau cover and measureably better than with gate removed or lowered.
If you believe lowering the gate helps your mileage you probably also believe frogs cause warts, or kissing a frog might turn it into a prince(ss) or any other number of things often accepted on faith but never scientifically measured. How about moth balls added to the gas tank for extra horsepower? Keep your razor blades in a small pyramid to keep them extra sharp for a long time. Junk science abounds! Remember all those TV advertisements last year for electrical muscle stimulators. Where did they go? Visit any auto parts store and for a good laugh look at the plethora of chemicals availlable to cure everything automotive. Some of the stuff may work some of the time in some cases but generally it is "snake oil", right up there with getting the x-rays "touched up" because you don't want to have the operation. What about putting aluminum foil in your hubcaps to foil police radar.
Pat
"I'm not from your planet, monkey boy!"
Pat, two things you've said got my attention.
<font color="blue"> "Auto makers do extensive testing these recent decades in attempt to keep the "fleet" average fuel consumption in check." </font color>
In the 70s, Congress mandated autos have a fleet averge of 27.5 mpg. They also mandated a fleet average of 20.5 mpg for light duty trucks (minivans, pickups, and SUVs). Legislation proposed this year is supposed to mandate improved mileage in light duty trucks. A 20.5 mpg average! We know its not met by the pickups, but those with the sloped nosed minivans know how the average has been brought up.
As for the auto makers, they gave us the Vega, the Pinto, among others, and this year have publicly advertised the quality of their vehicles in the past was lacking. They said this admission was doen to try and regain trust. Simply put, the major auto makers have about the same credibility as junk science. Believing them takes real faith.
You also said, <font color="blue"> If you believe lowering the gate helps your mileage you probably also believe frogs cause warts, or kissing a frog might turn it into a prince(ss) ... </font color>
It seems to me that when you drop a tailgate, you change the shape of your vehicle--and change it's aerodynamics. Some believe that aerodynamics affect mileage. At least in my thinking, it takes more faith to believe that dropping the tailgate has no effect. I can't say dropping the tailgate cause warts on a Chevy, or turns a F-150 in a prince, but to think it has no effect on mileage
Pat, I can agree with you whole hearted on one thing,
<font color="blue"> "A mediocre day in the country beats a GREAT day in the city!" </font color>
-Jonathan
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