The oil enters the filter through the periphery holes...not the big
center hole, that is the exit hole.  The anti-drainback valve is the
(rubber? or plastic?) "flapper" just inside the periphery holes that
keeps the oil from reversing it's flow out of the periphery holes when
the engine is not running (and the engine is enough off verticle to let
gravity have it's way).  Its an easy feature for which to check a
filter's having :)(I love it). The bypass valve is the spring-loaded
valve which is almost universally located at the opposite end of the
can.  Just wanted to add the clarification to Yau-Man's fine research.

-Dana-

> Now, some models of FRAM have anti-drain back valve.. but it is just a
> little plastic flap over the exit portal.  The ones in the Mahle/Knecht
> filter is a spring loaded metal valve.  Take a pick of what filters you want
> to use in your beloved Vanagons, but make sure it as anti-drain back
> valve... and the by-pass pressure valve is set correctly for the vanagon
> engine.
>
> Anyway, folks.. here it is.. do not use Rabbit/Golf filters in your
> vanagons. You can use Vanagon oil filters in your Rabbit/Golf.
>

>
> Yau-Man Chan
> 87 GL