[IamFODI]

Happy to help.

This isn't on you; just a rant about how oil analysis has been popularized. It's so oversold, and... mis-sold? Is that a word? It's talked about like one report can tell you everything you need to know about wear, which is completely false and possibly misleading in almost all cases.

It can be good for tracking wear if there's a likely failure mode that shows up in a clear way on oil analysis, or if you have perfect knowledge of the engine's metallurgy and oil's chemistry. And even then, you still need a history of samples at regular and short intervals, or you can't be sure what you're looking at. We definitely have the likely failure mode piece, but we don't know how reliably it shows up on oil analysis for any bearing other than the original BMW ones -- and even there it's sketchy because there have been engines with worn bearings but clean oil analysis reports; in other words, false-positives are rare enough but false-negatives aren't.

Beyond that, we have squat. Almost no one outside of BMW, Castrol, and Shell has anywhere near the required info on the engine's metallurgy and oil chemistry, and none of those parties will be sharing what they know any time soon. The manufacturers of aftermarket bearings will of course know the alloys they're working with, but you can bet everything you own that they haven't done a fraction of the necessary testing to figure out whether and how wear on their bearings shows up on oil analysis in this engine.

It's possible that other rod bearings (aftermarket and LCI) will show wear in a predictable way on oil analysis. Glyco, the manufacturer of the LCI bearings, advised me to look for Al and Sn trending upward in a (very) roughly 9:1 ratio. What we don't yet know are the false-positive and false-negative rates.

There are more expensive forms of oil analysis that go into FAR more detail about what exactly is in your oil. Those technically still require the aforementioned knowledge of metallurgy and chemistry, plus trending, to be truly meaningful. But in a pinch, a one-off of those methods is at least a step up from a one-off garden variety $20-$30 analysis.

In consumer car engines, what garden-variety oil analysis is really useful for tracking is:

1. Contamination, and
2. How the oil itself is holding up.

This includes the "wear" numbers because they can go high from acid buildup or highly active surface chemistry. So, if you want to see whether you're running your oil too long, or if your filters suck, or if your engine isn't running quite right, etc., oil analysis can be a good tool.

FWIW, I had LCI rod bearings put in shortly after I bought my car, and I'm doing oil analysis at every oil change. My thinking is that if I start seeing that 9:1 Al:Sn ratio, I'll plan for another rod bearing change then. But if not, I'll still plan to revisit the bearings after 60k-80k miles -- unless it becomes clear by then that clean reports reliably indicate low/no wear on these bearings.