What does oil analysis tell you?
Updated · Wingman AeroCare, KFNL
Short answer: Spectrographic oil analysis measures the tiny particles of metal and other elements suspended in your engine oil, in parts per million (ppm). Each metal points to specific engine parts, so rising iron, chromium, copper, or aluminum can flag wear in cylinders, the cam, bearings, or pistons long before a failure. A single report means little; the trend across several oil changes, compared with averages for your engine model, is what tells the story.
How does oil analysis work?
At an oil change, a mechanic draws a sample of warm oil (so contaminants are still suspended) and sends it to a lab. The lab burns the sample in a spectrometer and measures the concentration of each element. Many labs also test for fuel dilution, water, and insolubles, and some compare your numbers to averages for the same engine model.
The report usually includes:
- Wear metal concentrations in ppm.
- Contaminants such as silicon (dirt).
- Physical properties of the oil.
- A lab comment flagging anything unusual compared with your history and the fleet average.
What does each metal mean?
Exact sources vary by engine model, so treat this as a guide:
| Element | Common sources |
|---|---|
| Iron | Cylinder walls (steel barrels), camshaft, lifters, crankshaft, gears, rust from inactivity |
| Chromium | Chrome-plated cylinder walls and piston rings |
| Nickel | Valve guides and valves, some cylinder bore coatings |
| Aluminum | Pistons, crankcase, and accessory housings |
| Copper | Bearings, bushings, oil cooler; often elevated in new or recently overhauled engines |
| Tin | Bearing materials |
| Silver | Plating on some engine components, depending on model |
| Silicon | Dirt from induction leaks or a worn air filter; also some sealants |
| Lead | By-product of leaded avgas; normally high and not a wear indicator |
Why does the trend matter more than one number?
Wear metal levels depend on how many hours were on the oil, how the engine was flown, whether it sat, and normal variation between engines. One elevated reading can be a fluke or the result of a longer oil change interval.
What matters:
- A steady baseline across several samples means the engine is wearing normally.
- A sudden jump in one metal is a reason to look closer.
- A steady climb over several samples is a pattern worth acting on.
Because of this, the first one or two samples on a new engine or a new owner's engine mostly establish the baseline. The value builds over time.
What should happen after a bad report?
An elevated or rising number is a signal to investigate, not a diagnosis. Typical next steps:
- Cut open and inspect the oil filter for visible metal. Lycoming's guidance on filter and screen inspection is in Service Instruction SI 1492.
- Shorten the next oil change interval and resample.
- Borescope the cylinders. See what a borescope inspection shows.
- Check for induction leaks if silicon is high.
- Review engine monitor data for temperature anomalies.
What can oil analysis not tell you?
- Large metal chips are too big for the spectrometer to measure; that is why filter inspection matters.
- It cannot locate the exact part that is wearing.
- It cannot predict sudden failures that do not shed metal first.
- A single sample says little without history.
How often should I do oil analysis?
The most useful practice is a sample at every oil change, with the oil filter cut and inspected at the same time. Lycoming's oil change guidance (Service Bulletin SB 480) calls for oil changes every 50 hours with a full-flow filter or 25 hours with a pressure screen, and no more than 4 months between changes even if the hours are not reached, because acids and moisture build up in oil that sits. Consistent intervals make the trend more meaningful.
How Wingman handles it
Wingman AeroCare's Managed Maintenance Program includes oil analysis on every oil change, so your engine builds a continuous trend history instead of a few scattered reports. When a number moves, we work on Lycoming and Continental engines and do troubleshooting and cylinder and top-end work in-house, so we can follow up with the right next step. See piston engine maintenance or contact us.