This is coffee filter paper that a beaker of the first oil drained through; it's clear to see that there's plenty of fine metal in the oil, the oil filter nonwithstanding.



A friend of mine I talked about this with, having worked for a bearing manufacturer, told me about the very strict quality control procedure there concerning metal residues that might be left over from the machining process, and he found it quite possible that in this case this oil containing metal particles would be damaging to the bearings in the engine in the long run. I would definitely flush that out as soon as I could.

Still it is reassuring to learn that no significant problems have been noted with the standard procedure.

Just speculating, that might be because the hard metal filings coming from the crankcase (that could really cause damage) would indeed be efficiently caught by the oil filter, and this greyish matter still present in the oil, being softer metal (from the cylinder wall maybe ?) would not be so harmful.

If it came from the cyilinder, well that would mean my rings have set properly, wouldn't it ?