Malcolm,

One thing I noticed in the K&N literature is that they recommend that if the
filter is to be used in very dusty off road conditions... it should be
cleaned and reoiled more frequently... I don't remember them saying how
often... guess it's a judgement thing... also, as I remember, K&N recommends
that if you can not do a full clean and reoil job then you should remove
filter, tap it on something to remove loose sand, reoil outside of filter,
and put a fresh layer of oil on the inside filter surface... as I remember
this reoiling in dusty conditions is due to the dust absorbing the oil and
drying out the filter cloth... and thus reducing its effectiveness.... all
this from memory as I don't have the literature right now... so use your own
good judgement....

Also.... K&N sells foam prefilters for some models... unfortunately not for
the later model Vanagons.

Sounds like you're having a great time..

Bill Davidson

Bill