How much over 30 was it? 35? 300?
In general there are no “limits”. There are averages for the type of engine, based on what the oil analysis company has historically seen. But if your engine is a rare type, the average may be just based on your previous samples 
I was 60. Well, there’s a “recommended” limit, and that’s 30 for this engine, at least according to this lab. One year earlier before the starter drive failed it was 7, 4 months later it was 6 again.
60 is high but not outrageous and possibly means a piston pin plug is rubbing. One would probably shorten the next service interval to 25hrs and resample.
Mine was over 30 here and then came back down again
It was aluminum, and there is no AI in the piston plugs. I am sure it came from the starter adapter. All other metals were always very low.
Never.
That’s why I’m not a big supporter of OA: It does not give you actionable information, just a bunch of data that will have you fretting (no pun intended ) about what it all means !
In answer to the question at the top of the thread………Never !
The Q is whether there is a scenario where OA alone will indicate a major safety-critical problem, which would not result in metal in the oil filter.
I am sure there are scenarios where this is so. A bearing with not enough oil supply would be one, and they can seize up fairly suddenly once they get to a certain stage. One way you can get this is if somebody changed cylinders without re-torquing the crankcase bolts, and the crankshaft got moved.
For some reason we don’t hear of many cases. I think the reasons may include
So there are huge disincentives to taking drastic action. The normal process, upon finding something suddenly doubling, is to shorten the next oil change to 25 or even 10 hours and re-test.
The biggest problem is that our engines cannot be inspected properly without opening the crankcases. It’s a stupid design.
Isn’t the oil analysis and its results based on an oil change interval of 50 hours? I have no idea …
No; anything of say 10 or more will give you data.
Obviously there is no point in doing OA – or cutting open a filter – if it has just say 1hr on it. This is a risk on a prebuy check. The owner might have just done a service, possibly for just this reason. Or it could be a hangar queen which gets a 1h run once a year, between annuals. I knew of a 421C like that.
It will sure give you data, but the amount of materials in the oil cannot be comparable after 10 vs. 50 hours. I am sure that you have to test it in the same interval if you want to compare it.
