TBN is a useful number, but modern oils and engine design often result in lower numbers without the associated problems it used to indicate. What's missing from that report posted above is the TAN value, which is very useful in combination with TBN. Those values along with the bearing metals are needed to help figure out when to change the oil. Note that the capacitance, that the BMW oil life sensor reads, is a good way to decide when those values are approaching a problem level. TBN is no longer as critical a number as it used to be with looser original systems, higher sulphur levels in the fuel of old, and the stability of a synthetic oil versus a conventional one.
https://www.chevronlubricants.com/en...bn-vs-tan.html