I have something like this on my '99 EuroVan GLS called the Scanguage.
We sell them on our website.  They won't work on a Vanagon as they
operate off of OBDII.  It does work on most all vehicles 1996 and up.
It gives you mpg, fuel cost per mile and a lot of other functions.  It
gives you added gauges like transmission fluid temp, voltage and other
measurements it can get from your ECU.  It reads faults and resets your
CEL.  You just need to update your Vanagon to OBDII.

Steve
http://EuroCampers.com
636-337-7700
888-797-5994 - order desk
On Feb 17, 2008, at 9:07 PM, Wesley Pegden wrote:

> Something they mention that I've wondered about, is whether it would be
> feasible to install some sort of mpg display in a vanagon, that would
> monitor fuel usage and compare with speed.  I know the times I've
> driven
> cars with a mpg indicator, my mileage improved greatly as a got used to
> what the most efficient way of driving the car was.  I'm sure I'd get
> better mileage in the van with direct feedback.
>
> -Wes
>