I sent a used oil sample to a lab for analysis. No special concerns, I just wanted to see if there were any exceptions I wasn't aware of.

The report results were largely unremarkable (a good thing). Wear levels are not elevated, and no fuel or coolant contamination. The Moly was measured higher than average for this engine because the oil contained a bottle of Liqui Moly MOS2. There is a callout for low oil viscosity at engine operating temp, I'm not sure why this happened.

For comparison, an analysis of new unused oil can be found here:
https://pqia.org/castrol-gtx-high-mi...-30-motor-oil/

 

I remember when I used to do those for recip and turbine jet engines.

 

Aviation mechanics is very strict. Tightening bolts to torque is not merely a best practice, but essential. And mechanics can ground the aircraft if they see anything suspicious during an inspection. Also, if I recall correctly, this type of oil analysis testing is mandatory in many cases. They may even dissect the oil filter media.

 

Well, yes, things like proper torque of fasteners is important, but the definition of suspicious is very wide, and it's very different in general aviation as opposed to airlines, for example. Oil analysis is indeed mandatory in some situations, but not in general aviation. It's considered a damn good idea because it can give you early warning that something will fail, and the lab can even tell you what will fail based on what metals are found (i.e. high bronze content could mean a bushing is failing, etc.)

When I worked on a/c in the Marines I could in fact ground an aircraft regardless of my rank, but I was always told make sure I knew what I was doing and get a second opinion if I have any doubts. One time I was even asked to do it because the pilots and crew chief were dead tired and didn't want to fly (peacetime mission, of course).