"Jinx" wrote in message news:007001c7b90f$6cf2fbe0$0100a8c0@ivp2000... >> I drive with the tailgate down when I use the pickup unloaded. It >> does save fuel because up, it can scoop up enough air pressure at >> 50 mph to cause significant drag > > Mythbusters claimed that with the tailgate down, the vortex behind > the cab disappears. According to the pick-up manufacturer (smoke > trail test film), air coming over the cab roof bounces off that vortex, > resulting in less drag > > http://www.cartalk.com/content/columns/Archive/1997/October/05.html > > As they say there, it's counter-intuitive > > Not that I'm doubting your results, you know your vehicle and > have the numbers This was known to be true before Mythbusters, but it is a bit counter intuitive and may not apply equally to all makes and models due to different bed lengths and other small design changes between models. Small changes can do big things to aerodynamics, especially if a small change moves where a boundary layer is tripped to turbulent flow. As far as the show goes, I thought they had a Ford engineer on there explaining the effect. I'd expect modern vehicles like the newest Ford F150 to be designed to get the best mileage with the tailgate up. But even better than tailgate up or down would likely be an aftermarket bed cover. Jeff -- "They that can give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety" - B. Franklin, Bartlett's Familiar Quotations (1919) -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist