On my 85 westy, I just replaced the low pressure sensor with a new
one (the 0.25 bar model).  Now, the oil pressure is on when idling at
900 rpm (when hot), but goes off at about 1100 rpm. (with the old
sensor it took 1400 rpm to get it to turn off).

I'm running 20w50 with stock VW filter.  Engine has 144K miles.  I
assume this means the lower end of my engine is wearing out.

Questions:

(1) Should I worry about this?

(2) Short of a rebuild, should I do anything?  Any additives to
thicken the oil?  Run straight 40-weight or perhaps a mix of 20w50
and 40w?

thx!