On Wed, 21 Jan 2004, Karl Ploessl wrote:

> Sean asked:
>
> What is the capacity of a 81 Westy (stock).
> My gas gauge does not work and I think my mpg just dropped from 17 to
> 14 after a tune up.
> --------------------------------------
>
> according to the "vanagon specifications" (for 1981) the fuel tank holds
> 15.9 (US) gallons (60 liters)

However, if you need the tank capacity to do mpg calculations, you're
probably doing them wrong.  Here's what you want to do:

- Fill the tank completely.  Reset your trip odometer.
- Drive a couple hundred miles.
- Fill the tank again, at the same pump if possible.  Use the same
  procedure.  (i.e., if you stopped at the first shutoff the first
  time, stop there again.)
- Note how many gallons you added.  This is how many you used since
  the last fill-up.  Divide the reading on the trip odometer by
  this number.

The pump shut-off is not always consistent, so it's best to do this a few
times and average the results.  On a car that I've just bought, or that
I'm planning on doing engine work on, I'll often actually keep a running
log of the fuel economy for every tank of gas I buy.  This can be really
educational about your driving style and the effects of any repairs you
do, as well as giving you an idea about your engine's relative state of
tune.  A small notebook is excellent for this, or if you carry a PDA there
are free software packages that will do the job for you.

David Brodbeck, N8SRE
'82 Volkswagen Diesel Westfalia
'86 Volvo 240DL wagon