Dmace
Elite Member
Actually, the Mythbusters test was to prove if leaving the tailgate down on a truck gained gas mileage. What they proved was that the truck with the tailgate up and no tonneau cover got better gas mileage than the same exact truck with the tailgate down.Spiveyman said:Myth Busters did a show on the tonneau covers and said it didn't increase fuel mileage, that an open box atually had the best fuel mileage. I'm not saying this is fact, just saying what I saw on TV (so it must be true right, like reading on the internet - it's all true.) I got a small boost in my F150 by adding a bed cover, at least I think I did. But maybe when I'm watching my mileage I drive better too.
The result was that with the tailgate up, wind created a low pressure in the bed of the truck which then acted as a tonneau cover and created less drag. With the tailgate down, the wind would pass right through the bed and put down pressure on the tailgate like a wing and create more drag.
The truck with the tonneau cover got better gas mileage than both but it did prove leaving the tailgate up is better than down with no tonneau cover.