O360-A4A if I had to wager.
750 hours since last over haul.
The thing to keep in mind is an oil analysis is only one of the tools to maintain your engine. It is not a diagnostic tool per se. There have been a few threads on PoA that go into more detail on how those different tools are used. Perhaps look them up.
If the answer was always that, then I'd agree, but "might be worrisome" and "is clearly a problem" are two different things, and oil analysis can show the latter.
It's possible, I guess, but under what circumstances would you expect to find "clearly a problem" on the oil analysis, accompanied by normal oil usage, nothing concerning in the filter, and a normal borescope?
The "clearly a problem" should prompt you to look deeper than that.
The oil analysis provides an indication to a potential problem way before you see it in the filters or scope. It simply gives you the ability to minimize collateral damage and fix the problem while still contained.
Would you hate it if the owner/seller had a oil analysis for every oil change from the beginning on a engine you were considering buying?
A single report doesnt offer much. Also multiple reports from samples taken by different methods or different engine locations can lead to skewed trends which can take you down the wrong path.
I've found the lack of oil analysis use at the Part 91 private/rec level is more due to a lack of education of the benefits. However, once those benefits are demonstrated and how the analysis fits into the overall picture on engine health they will subscribe to it. Some didn't but it was usually due to having a high time engine which provided a limited benefit at that time. However, once the engine was changed they would sign up for the analysis. But, the same could be said for Part 91 owners on regular prop balancing too. Preventative mx covers a wide range of tasks that to an engaged owner can make the difference in the long run.
One problem is that oil analysis can give both false positives, and false negatives. It can show high metals when there is nothing wrong, and it can fail to show anything when there is something wrong. This is true even with long-term trends.
Interesting. But that's not been my experience at all even after dealing with 100s of analyses across a number of different platforms. While I have seen skewed results, over 95% were due to external sample variations or contamination of the sample. Regardless, based on my experiences, I still recommend oil analysis as part of a regular monitoring program for any aircraft.
Not in my case. I took every sample from an engine still warm immediately after flying, mid-drain (not near the start nor end), directly from the stream of draining oil into the sample container.
My advice is to treat the patient, not the lab results. If the engine has no symptoms: easy starts, good power, good compressions, clean oil filter element & screen, oil consumption - 1 qt every 15 hours is perfectly healthy, borescopes during annual look good, then keep flying and don't worry about it. When the engine gets tired and time to overhaul is approaching, you won't need UOA to tell you because the engine will tell you in other ways that are more meaningful & reliable, like reduced power and compressions, increased oil consumption, etc.
