At 04:01 PM 10/20/2009, David Beierl wrote...

>Half-full is how the gauge has behaved on both my '84 and '89.  Do
>you really think that der Volks at VDO would put significant-looking
>marks on the gauge for no reason?  We're more used to them putting on
>tiny insignificant-looking marks that are intensely meaningful

My '81 (both sender and gauge were tested/calibrated according to
Bentley when I replaced the tank) hits the first mark at about 75-80
miles (I get 19-20 MPG), and the second at about double that. Note that
all the marks are the same length, _except_ the second one which is
shorter. That's all consistent with the smaller mark being 1/2 tank.
The gauge is non-linear, it drops much faster near full.

Perhaps they changed the sender on later years so it reads more
linearly.