"Don Gourlay" writes:

We used Blackstone for a couple of years. They alerted us to the fact that
the aluminum content had shot up. Ended up doing a top overhaul. Previously
the leak down tests were ok. We had heard this can change quicky which it
did. The analyiss was the trigger. AME said things would be been fine for
about another 100 hours but we did the top anyway.

A lot of people on the field laughed at doing the analysis every oil change.

Don--

I have an Aircoupe with a C-90 engine. First airplane owned so I'm
still learning. OK, my mechanic is skeptical of lab analyses, and
prefers examining the oil and filter after each change. Best would be
to do both, but my question to you and others is--

If you could only do one thing: either lab analysis of oil after each
change, or your own visual examination of oil and filter after each
change, which would you do?

In your above scenario where the lab alerted you to a problem, would
you have noticed the problem by doing a visual inspection of oil and
filter--like seeing metal particles?