Peter Dohm wrote:

I, for one, am not convinced that a p/u has less drag with the gate
closed--although I concede that many trucks may gain a trivial benefit at
some particular speed.


Why is it so hard to believe. You have seperated flow, and seperated
flow equals high drag. Put the tailgate down and you have one huge drag
chute in the form of the cab. Put the gate up, and you get an air dam
in front of the gate that sort of creates an airfoil from the top of the
cab to the top of the gate. You've still got a big drag chute, just not
as big as before.

Someone smarter than me said that how you meet the air isn't as
important as how you leave it.