Might I suggest that unless you are doing thousands of miles a week then
these sort of 'estimates' of fuel consumption are hopelessly inaccurate. I
have tried to make this point about 6 months ago when I joined the list, but
to no avail.
The biggest factors that affect fuel consumption are ambient temperature,
wind and driving conditions, the engine's vagaries being easily secondary to
this unless the thing is 'obviouly' running appallingly - in which case, the
query would be of another nature.

To do a good few hundred miles 'around town' , unless you mean 'around city'
without intrespersing any other journeys would perhaps be rare, and we all
know that only on the open road do milesper gallon mean much, as opposed to
gallons per hour.

I would suggest that the odd drop in consumption is more likely to be a
fill-to-fill error eventually making its presence felt, unless you are
actually using a pipette to fill the tank.
If you plot 'fill-to-fill' and 'running-mean' figures against mileage on an
Excel or similar chart then you should see these trends balance out....

..unless you've got a leaky fuel filler pipe (syncro), overfill the tank,
use different filling stations and pumps or have leaky/drippy injectors and
let the vehicle idle a lot.

Clive
'88 Syncro Transporter
----- Original Message -----
From: Mike Miller <mwmiller@CWNET.COM>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Thursday, December 05, 2002 4:07 PM
Subject: Gas mileage

> Volks,
>
> Every once in a while my gas mileage drops 20+%, from 18 to 15 around town
> for example.  Then it will go back up.  Nothing done to van.
>
> Checked O2 sensor and it's OK every time.
>
> Any ideas?
>
> If it's bad grounds can I just shoot the damn thing and be done with it?
>
> Mike
>