"cavelamb himself" wrote in message
link.net...

It is more fuel efficient to drive a pick-up truck with its tailgate
down, rather than up.

Busted

Driving with the tailgate down actually increased drag on the pick-up
and caused it to consume fuel faster than the identical truck driven
with the tailgate up. It was later revealed that the closed tailgate
creates a locked vortex flow that created a smoother flow of air over
the truck. With the tailgate down, the trapped vortex was dissipated and
the drag increased.




http://en.wikipedia.org/wiki/MythBus...%29#Blown_Away

Somehow, that is even harder to accept, as a general statement, than the
original assertion.

It has not been proven either way, from my experience.
When I had a 1977 Toyota pick-up, I tried it and could not prove any
difference at all; so I went back to driving with the gate closed--because I
felt that leaving it open defeated that purpose of having a rear bumper.
OTOH, a know two owners of late 1990s full sized Chevy pick-up
trucks who both swear that it adds between 1 and 2 mpg. One of them, who
only occasionally loads cargo in the bed, simply leaves the tailgate at home
when not in use.

I must suggest that different trucks may have different results, even when
tested at the same speed, and that the biggest improvement of all might be
from driving the other car when there is nothing to haul. Then again, if
you have only one vehicle, there is a damned good case to be made in favor
of the truck!

Peter