Oil filters:  Mann, Mahle, yes, but don't forget Amsoil.
Another oil filter that works very well in the vanagon is made
by Amsoil. Especially if you are using synthetic oil
with longer drain interval, this filter could benefit you.
( I still change the oil every 4000 miles. old habit I can not
break)
I have used the Amsoil full flow spin-on filter on my
westy for a couple of years now with no problems.
The oil light goes out instantly at startup, and never
flickers. No more hydr.valve lifter ticking. Even when
I start the van after several weeks of storage.
The filter for the vanagon is the  SDF 34 .
I ordered four or five, and got a discount from the
local dealer.
They are not cheap. something like $7 or $8 per filter,
but they appear to be well made.
Some of the features:
oil pressure relief valve, heavy duty case of drawn steel,
cellulose, synthetic, and glass blend media, and anti-drain back valve.
Check out the info on the links.
http://www.amsoil.com/products/sdf.html
http://www.amsoil-oil.com/asf.htm
Harald
90 westy