[airguy]

I've been getting oil analysis done on my airplane since we bought it last year (4 samples every 50 hours so far) plus 3 from previous owner, so I'm at a point now where I can do some useful trending of the metals found in the oil. Does anyone have handy a description of the sources of the various metals in the engine to identify a particular suspect for elevated levels of each element?

 

[DakotaHawk]

My oil analysis comes back with each of the contaminants highlighted in green, yellow, or red. As long as you're getting everything in the green, there's no reason to worry. When you get a warning yellow, then it's time to take your analysis to your mechanic to check it out.

 

[DanBaier]

Common sources

This may be a little dated - I have it in my files from a few years ago.

Iron - Cylinders, rotating shafts, valve train and any steel part sharing the oil.

Copper - Brass or bronze parts, bushings, bearings, oil coolers, sacrificial coatings.

Nickel - Valve guides, trace element in steel, some cylinder types.

Chromium - Rings, cylinders, a trace element in steel.

Silver - Sacrificial coatings, a trace element in some types of bearings, bearing cage plating

Magnesium - Engine casings, additives

Aluminum - Pistons, piston pin plugs, bearing overlay, casings.

Lead - Primarily leaded gas blow-by, traces from bearings

Silicon - Abrasive dirt from intake air, silicone sealers and gaskets, sample contamination.

Tin - Bearings, bronze parts (with copper), anti-wear coatings.

Molybdenum - Traces of anti-wear coatings, some cylinder types, and bearings.

Also, I've heard, but not personally seen, that higher than normal copper can be due to using Aeroshell Plus causing some copper plating to come off some internal parts (ie., camshaft) - the copper plating was to protect those areas from nitriding and if this happens it's not really a problem although it might seem like one.

 

[airguy]

Also, I've heard, but not personally seen, that higher than normal copper can be due to using Aeroshell Plus causing some copper plating to come off some internal parts (ie., camshaft) - the copper plating was to protect those areas from nitriding and if this happens it's not really a problem although it might seem like one.

Interesting - my copper content is the only one that has risen over the last 200 hours (when we purchased the plane) and last sample is 12.2 ppm. That's still well in the good range but is higher than the 3-4 ppm range that was being seen by the previous owner (don't know what oil he used). We are running Aeroshell 15W50 and I'm wondering if that is the reason. The number has been very stable over the last 4 samples, so I'm just watching the trend at this point.

The engine appears quite happy at 653 hours, only consumes a quart of oil about every 12 hours and oil filters are very clean, I'm just wanting to keep another diagnostic tool active to alert me to a problem before it becomes an airborne problem.

 

[Low Pass]

Dan has provided a very comprehensive listing of sources for your components.

Couple of thoughts - watch for the trends and look at everything collectively. Absolute individual component numbers are only one piece of the analysis.

If you just want to spend money and have more info, go for the wear particle analysis. Unless your running a Rolls Royce Merlin, I wouldn't do it.

I like to watch/trend the physical properties as well. Total acid number, water and viscocity. And last, you have to be very consistent with sampling method, timing, and lube oil used to get full value out of oil analysis.

FWIW - A portion of my professional background is industrial machinery reliability engineering and consulting services.

 

[dedgemon]

Yep

Interesting - my copper content is the only one that has risen over the last 200 hours (when we purchased the plane) and last sample is 12.2 ppm. That's still well in the good range but is higher than the 3-4 ppm range that was being seen by the previous owner (don't know what oil he used). We are running Aeroshell 15W50 and I'm wondering if that is the reason.

Yep, its the Aeroshell multigrade. I saw the same thing a few years ago on my RV9A. Switched back to Phillips (all mineral) and it came right back down.