At 05:00 PM 12/12/2010, Roland wrote:
>So I installed the Mann filter and drove for 1/2 hour or a bit more, uphill
>downhill, fast, slow.  Not a hint of the oil light/buzzer.  That makes the
>total of changes as the Mann filter plus 20W50 oil.  So I am going to call
>this resolved since there isn't any further work I feel I should do unless
>it reoccurs.

This is a bad idea, unless you and your Vanagon both believe in magic.

>Is this conclusive?  To Dennis' point, no definitely not, since we never
>identified the root cause, and really can't without the pressure gauge.

As Dennis has pointed out, the oil filter can not fix this
problem.  If it's clogged it could hide the problem, but it cannot
possibly fix it.

>There may have been some other cause that coincidentally went away during
>this time period when I was "exploring" solutions with the oil/filter
>changes.

Yes, there could.  Can't think of any that would be good news, so if
that's the case I would think the best possible thing would be for it
to come back so it can be fixed.

>   Not conclusive, but regardless it is pretty strong evidence that
>there is something about the filter brand and oil weight.

No.  Oil viscosity, absolutely - but you said that helped but did not
cure the problem.  Filter, absolutely not.  This is a rock-solid
*fact* and you have to face it.

Measure your oil pressure.

Yours,
David