Oil analysis

Richard O

Richard O

Pre-takeoff checklist
Joined
Oct 27, 2006
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259
Location
Marietta, GA
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Display name:
Richard O.
I'm going to look at a Super Decathlon tomorrow that has a low time (260) SMOH. Can you learn anything about an engine from a one time oil analysis. I was thinking about asking for an oil sample and having it checked.
 
You can't tell much from a single sample (unless it's extremely contaminated) . You need a history of wear analysis to draw any conclusions.
 
The oil analysis is good for looking at trends over a number of hours. With a Lycoming engine the best, on the spot check for problems is to check the suction screen and cut open the filter for a closer look. I have a Mirage in the hangar right now that suffered a main bearing failure. The oil analysis looked good, the engine ran perfectly, no problems! We found bearing material in the suction screen and a trace in the filter. Critical material like this wont stay suspended in the oil after shut down to be drawn with the sample. The pieces are so large that the suction screen stops them first. I have seen so many aircraft through the shop that had 500 hrs and the screen safety wire hasn't been touched since the factory.

At a pre-purchase inspection or annual we will send any material we might find to Lycoming for evaluation. There was one point in time that 1/2 of the materials we sent in resulted in a tear-down and repair. Its much better to find this out before you buy. If the aircraft has had little use it's a good idea to check the cylinders for rust too.

Good luck, Kevin
 
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