Oil Samples Show the State of Your OilProfessional Skipper Magazine Issue 37 Jan/Feb 2004
Oil analysis, or more importantly 'used oil analysis', offers a very good way of looking into your engine without removing a bolt. Dismantling your engine to inspect the bearings and/or bores for abnormal wear is a very expensive and time-consuming task. At a fraction of the cost used oil analysis is the only other way this can be done. By inspecting the used oil you can get a very good indication of what is going on within the engine and/or transmission.
By removing the dipstick a 125ml sample of oil can be drawn out without having to drain the oil. This is very advantageous as oil samples can be taken between oil changes. To do this a specific piece of equipment is required. However, the way the sample is taken is very important, as the results can be dramatically affected. The most important point here is that the engine or transmission to be sampled is up to operating temperature or at least run for 15 to 20 minutes before the sample is drawn. This enables the oil to be completely stirred up so that the sample is a good cross representation of the whole piece of equipment in question. Oil evacuation pumps on the side of engines should not be used as they could contain large amounts of sediment, which may not have any relevance to the equipment. If there is no choice then a large amount of oil should be drawn off first before the sample is taken. After which the oil can be put back into the engine.
Once the sample or samples are drawn then they can be sent off to the lab for analysis. A good turn-around time here is essential. Results should also cover a number of areas namely wear-metals, contaminates and oil quality reserves.
I find that my customers' main concerns revolve around the wear-metal results. The report should include wear-metal counts for aluminium, chromium, copper, iron, lead and tin. However, contaminates like water, fuel dilution, soot, sodium and silicon should also not be forgotten. All things being equal, if your equipment is kept free of these contaminates the wear-metal counts should remain low and not become a problem.
The oil quality reserves are also an area that is quite often forgotten about. Basically the oil quality reserves relate to the remaining additive package that is still left in the oil. Anti-foaming, anti-wear, anti-corrosion and suspension additives are all added to the base stock to build up a high quality oil. The measurement of these is normally represented by the TBN (Total Base Number) and zinc results. By looking at these results the length of your oil service intervals can be more accurately measured. This enables the oil to be used more economically i.e. less oil changes, less waste oil and less service costs and downtime.
If you are not use to receiving or reading these types of results from the lab then the figures can be quite daunting to understand or interpret. There are many combinations in the results that could point to a problem. Also, certain figures have different levels of alert so determining if there is anything wrong or not could be very important.
Basically there are two levels of Alert. The first is a 'warning' (+), which alerts you to the fact that the level or count is just above or in some cases below normal or acceptable limits. The second is an "Action" (*). This highlights the need for possible further inspection. However in saying this, a marine installation throws up a number of these that are completely normal and acceptable i.e. copper in engines for instance. What can appear to be an unusually high copper count can in fact be attributed to the engine's oil cooler pipework and as such is not of any consequence. Copper and lead in transmissions can also show some very high counts especially as the oil gets older. These high counts however can be directly attributed to the wet clutch packs within the transmissions.
Wear-metal results, or combinations of, in engines can generally be attributed to certain areas i.e. aluminium, chromium and iron may point to wear from the pistons, rings or bores, while copper, lead and tin by and large come from the main and/or big-end bearing shells.
Diesel and soot contaminates have the ability to greatly reduce the effectiveness of the oil to do its job. This can lead to a reduction in the oils serviceable life. Fuel dilution is a direct result of either injector, internal fuel line or pump seal leakage. As the percentage of diesel in the oil increases, the viscosity (oil thickness) of the oil drops, thus reducing its ability to protect and seal the engine.
Soot on the other hand increases the oil's viscosity, thus reducing its ability to flow around the engine. This can be very detrimental especially during start-up when the oil is expected to flow from the sump up to and around the top of the engine. High levels of soot can be attributed to a number of reasons, namely over-fuelling, over-loading or excessive blow-by.
Other contaminates like sodium and silicon can also increase the oil's viscosity. Silicon is normally the result of dirt, dist or sand entering the oil or silicon greases or sealants used during routine maintenance, while sodium is the result of residue, either from saltwater or a glycol anti-freeze leak. While the sodium may remain, the water that it came with may not. This is because the high operating temperatures of engines can cause the water to evaporate off, thus leaving just the residue. However, large amounts of water may also emulsify in the oil causing it to look milky.
Used oil analysis offers you a preventive maintenance programme giving you the tools to decide when you alone, not your equipment, want the down time. The results enable you to programme your maintenance, hopefully during your off seasons. While one-off samples can be done, trend analysis of samples taken over a long period of time offer the best opportunity to view what's going on in your engine and/or transmissions. Samples should be taken just before your scheduled oil changes, however if need be they can be drawn earlier.
Written By Kelvin Hieatt
Managing DirectorMarine Diagnostics Ltd
