Mike,

Before you give up on the engine due to low oil pressure at idle you may
want to find an Amsoil dealer and try the engine flush.  It is the most
effective flush by my experience and fixed my low oil pressure problem at
idle.  In my case it was a sticky oil pressure relief piston.  I installed
a new piston and spring before trying the engine flush but this only
improved the problem partially.  I believe the flush removed residual
varnish from the casing bore that caused even a new piston to bind.  Two
years later the oil light has yet come on even once at idle regardless of
temperature.

I also switched to Mobil 1 from Castrol Syntec since I had the same problem
with a BMW with the same mileage on it and I used Syntec in both vehicles.
I replaced the oil pump in the BMW since the pressure relief valve in
integral to the pump to fix the problem.  I noticed a varnish buildup under
the valve cover of the Beemer during a valve adjustment and I even though
there was no trace of sludge or evidence of engine wear I figured the
Syntec may lubricate well but may promote varnish buildup during extended
drain intervals.  So far so good two years later with both vehicles on
Mobil 1.

Bill
83.5 Westy

BTW, I am not an Amsoil dealer, just a satisfied customer.

> The situation:  85 westy automatic, 150k miles, automatic, CA emissions.
>
> - When warm, low oil pressure light comes on under 1100rpm.  I'm
> running 20w50 with a good filter and it has already had the 0.3bar
> switch mod.
>