Some people drive their pickups with the tailgate down hoping their truck uses less gas per hundred miles. Does it work? First of all, the best solution is to get a truck bed cover. That will do the most to reduce air drag. But if getting a tonneau cover is not in the cards, should you put the tailgate down or up? According to a study done by the Society of Automotive Engineers, the answer is to keep it up.
The study found that lowering the tailgate generated more aerodynamic drag. It also reduces vehicle handling by increasing aerodynamic lift. This leads to less traction with the road. Besides the extra lift having the tailgate in the down position makes it easier for air gusts and crosswinds to turn the pickup to the side of the direction it is driving. These effects were found to be small, but they add up to burn more gas and reduce handling. So if you have to choose between tailgate down and tailgate up, leave it up.
You do have another choice though. It could be the case that for given conditions of speed, crosswind and so on the best position for the tailgate is somewhere between up and down. You can install a system which automatically positions the tailgate dynamically according to current conditions to minimize drag. Watch the video to learn about how it works!