This is more for diesel drivers, Vanagon or otherwise.

What is your MPG as it relates to the current cost of gas? In other
words, what kind of fuel consumption would a gasoline car have to
achieve to cost the same amount in fuel to drive?

I put up a simple page here to help you calculate it:
http://www.knology.net/~vw/relative_mpg

As of now, at $2.49 diesel and $1.59 RUG, my Beetle TDI gets a
relative 29 MPG.   A Vanagon TDI might get 30 MPG but its current
relative MPG is 19.  As price of fuel fluctuates, so does your
relative MPG.  Back in May of 2006, my Beetle got relative 47 MPG.
:-)

--
Chris S.
Disclaimer: "Death and serious injury may occur"