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]
Here's another "theory" I heard was that with the tailgate up it acts to direct the wind towards the cab and pushes the truck or creates pressure just behind the cab and pushes the airflow up to the top of the tailgate.
"Theories" are great aren't they!!!! How many of you are gonna go to sleep tonight thinking about that one. [img]/forums/images/icons/smirk.gif[/img]
Mike
Here's the answer.
improving the aerodynamics of a 97 dodge p/u
I think I've seen that paper and it kind of ticks me off. Not for their research but because my Prof talked me OUT of a very similar study nearly 20 years before that. And they got the 1997 American Society for Mechanical Engineering Young Design Engineer's Paper Competition International Award for it. My hat is off to the authors [img]/forums/images/icons/smile.gif[/img]
Rob
I would have expected all the results except the one with the tailgate off - just goes to show there's always something new to learn!!
Gregg
Remember - If I sound like I know nothing about farming it's because I really don't!
Thanks for that link.
Well, I'm not sure what to think of that article. It makes sense, but I have some results that don't match theirs. I drove my 1989 pickup for 11 months before I put a cab high aluminum topper on it. I keep careful records of all my vehicles in a little notebook that I keep in the glove box. I drove 9547 miles the first 11 months and averaged 17.8 MPG. This was just my rural drive to work and other driving around the area where I live. After I put the topper on it, I drove it the same as before, but also went on 3 highway trips and in the next 11 months I put 10,811 miles on it and averaged 18.1 MPG. If I take out the mileage from the highway trips, the average is 17.8 MPG. So, my results show the mileage to be the same with or without the cab high topper.
I'm going to be putting a fiberglass tonneau cover (which I ordered a month ago) on my 1999 pickup. So, I've got some mileage records of it before the tonneau cover, which includes 1 highway trip. After I've driven it about the same number of miles, which should also include a highway trip (if we stick with our current plans for this summer), then I'll post the results of that test.
So far, it's looking like it doesn't make much difference either way.
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