dont have the equation handy but the trick to the equation is that one of
the figures is a square.  it is squaring a relatively small figure that
changes with speed.  the trick is when that square becomes significant.
the coefficient of the vehicle determines that.  our vanagons are about
.81 (a flat surface being a 1.0)  the amount of HP needed changes with the
equation.  the more HP the more fuel needed.
rolling resistance
air resistance
gravity
vehicle frontal
are all in the equation.

with a stream lined vehicle weight will be more critical than with a
vehicle like our vanagons that are almost flat frontal.

300 lbs to a vanagon equation will be minimal.  300 lbs to a standard car
will ve much  more critical,
jimt
> Yes, I agree that wind resistance is a big factor, but a Westy going at 45
> mph is consuming much less energy than a Westy going 65. That's the point
> I
> was trying to make.
>