Oil Analysis

I finally got around to sending in my oil analysis from last year and sent along the most recent sample taken on my last oil change.  The first sample was from the total engine time of 35 hours and I had the screen and no filter.  Sample two was taken post filter add on, now running at fifty hour intervals and total time of 173 hours. All the numbers look good according to the report but I want to learn more about what the averages should be for my engine, the Lycoming O-360 A4K. I am a member of the Beech Aero Club (BAC) and I did manage to find some useful info for averages. After reading I find that the universal averages are a mix of all the different types of aircraft oil available. Therefore, the additives that are present in my sample will not match those in the universal averages column.

All my numbers look good with the exception of Iron and Copper. There are a few reasons for the higher numbers, although the trend shows a drop in copper between changes. I need to investigate the Iron numbers. I should also note I am running Aeroshell 15W50 oil and some folks say that tends to produce higher copper numbers.

Most Common Sources of Wear Metal Elements in Oil:

• 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.

One tid bit of info I read is reflected in my copper numbers. Copper: These metals are normally from bearings or bushings and valve guides. Oil coolers also can contribute to copper readings along with some oil additives. In a new engine these results will normally be high during break-in, but will decline in a few hundred hours.

I will continue to research the Iron numbers and discus the report with Roger at Cecil Aero, 08Romeo's real caretaker.