Oil pressure question.

Background:  Zippy is taking us on a 1500 mile trip From DC to the Catskills, then to western North Carolina (big mountains, for us in the east), then home.   Zippy
is a 1985 Westy GL camper with 190,000 miles, new VW heads 9 years ago at 95,000. This will be its last trip (I think) before prophylactic engine replacement.  I
have had a head leak for 3 years, and have some leaky engine oil seals.  Aside form the leaks, this engine is as reliable, smooth and peppy as it ever has been .

The biggest cause for concern is oil light after highway driving.  It has been doing this for several years, generally only at first idle after prolonged highway
driving.  Today it started coming on more than I have previously seen, during heinous stop and go highway driving.  It stayed on sometines for a few seconds even
with the van idling at 900rpm, and that seems new to me.

The van had an oil change 500 miles ago, and in that time it only used 1/6 quart, maybe.  The mechanic put in 10W40.
I have 4 business days before departure.

Questions:
Should I put in 20w50?
Should I have the oil pressure checked?
Does this lead to catastrophic failure in a 1.9 the way it seems to in the 2.1?
Any advise on what preventative maintenance to do?  Spare parts to bring?

I have read the FAQ on this on vanagon.com, but have not been able to search the list archives.  Is something wrong with them or with me?

Please cc any reply to vw85westy@aol.com