re: [I]The copper washer is for the drain plug on the crankcase

I already had those from another source, but certainly thoughtful of them.

re: Is it possible that there's something wrong that could inflict the same damage on your new filter? Are you tempted to check it before it is time to replace it?

Yep, I think I will be attending to this more frequently. The holes are symterical, so perhaps some of that fine "imported" quality control. I don't think there are particles in the oil making the holes.

And after I drove about 40 miles the oil PSI drops to 1.5 bar at idle, but a smoother swing now.

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91 300 TE 235K
93 Cabriolet 155K sold
92 300 TE 200K boneyard