My oil light flickers after long highway driving.  Which is more likely to look at if its loosing pressure.  This is a reconditioned engine, having about 90k in it.  Maybe they did not change bearings at all and I could change at least the conrod bearings without splitting the case.  This is a 1.9 engine and as I know, they need to be line bored after splitting.  
Or should I use some even thicker oil?  What kind?
Anyone?
Zoltan