[CarpenterGuy]

let it down. there's less wind resistance with it down so i would assume it wouldn't hold the truck back as much. but that just rounds off a small part of the brick

 

[CarpenterGuy]

myth busters did a test both ways . tail gate up won. creating a vortec thing was right.

They re-tested it because of veiwer complaints and it turned out that tailgate down was more efficient.