So, to help out an oil-dork, what should the numbers be for a multi-vis, say, RTS 5-40?
Blackstones will give averages for most engine types for you to compare results to. For a 1.9 TD I would not be too concerned until the Iron was over 50 ppm, Aluminium over 10, Chrome or Lead over 5 and Silicon from the air filter over 20.
The 5W/40 figures for a UOA are as follows:
SUS Vis at 210F: 66 - 78
cSt Vis at 100C: 11.9 - 15.3
Flash in F: > 410
Fuel % < 2
Water% < 0.1
Insolubles: < 0.8
TBN: > 1 (Normal) >3 (Severe service)
The trend is as important as the actual figures for wear metals, as every engine is subject to different use and to complicate matters you might have a temporary particle streak occur and rebuilt or new engines produce different figures.
The car should be driven at normal speeds for half an hour plus before draining the oil and the sample taken mid stream into a clean container.