On Mon, Sep 28, 2009 at 12:18 PM, Old Volks Home <oldvolkshome@gmail.com> wrote:
> And why would anyone use a bypass oil filter when both air and waterboxer
> Vanagons have full-flow oil filtration? �Just curious......

Using a bypass filter in addition to the full-flow filter provides a
way to filter much smaller particles from the oil.  The stock filter
is a compromise; it filters poorly enough to enable sufficient flow to
the bearings and has a bypass valve that permits oil to flow around
the filter media when flow is insufficient for proper lubrication.
Much finer filters are available that will not flow sufficient oil for
bearing lubrication.  Combining the two systems enables very fine
filtration with sufficient flow for the bearings.  I won't say
anything about the cost-effectiveness, only that it is possible to
filter much more of the fine particulates from the engine oil than the
stock system can support.

-- 
Michael Snow
1982 Westfalia 1.9TD
http://slowmachine82.blogspot.com/