Operators of trucking fleets and commercial vessels, regularly incorporate oil sampling and analysis into their preventive maintenance programs. Yet, oil analysis has never prompted much interest among pleasure boaters.
This lack of interest stems from two interrelated factors. First, a failure on the part of boaters to grasp the potential benefits of oil analysis; and second, an apparent reluctance on the part of the various oil analysis laboratories to solicit business from the general public. This reluctance, in turn, results in no efforts being made to educate the public about oil analysis, which only perpetuates the lack of interest. Both sides are missing out on an opportunity.
In trucking and heavy equipment applications the engines are expensive, the service life is hard, and the cost of repairs and downtime is high. If we turn to commercial shipping and fishing, the engines tend to be even larger and more expensive and the cost of maintenance and downtime even higher. Any predictive tool that can detect developing problems and headed them off early, particularly a tool that is cheap, is going to be cost-effective. Oil analysis, at $10 to $15 a sample, is just such a tool.
What about pleasure craft? Much as in a car, the engines are relatively small and not run particularly hard. Oil analysis is never routinely performed on car engines; why should it be done on boat engines?
We have an immediate clue when we consider that most modern cars will run 100,000 miles or more without engine problems. If we assume an average speed of 30 miles an hour, this translates into 3,333 hours running time. There are very few sailboat engines, and not many powerboat engines, that run anywhere near this number of hours without problems. In fact, it is not uncommon to see sailboat engines being torn down for major repairs after less than 1,000 hours of engine time.
The fact is that the operating environment for engines in pleasure boats is generally, from the point of view of the engine, atrocious. Many engines are cranked infrequently, run at light loads for a short while, and then shut down before being fully warmed up. Engines have to operate using questionable fuel (high sulfur content, see below) from pumps with poor dockside filtration. Bacteria, water, and, worst of all, salt water are often found in fuel tanks. The engine often has to breath salt-laden air much of the time, and it probably has a salt-water cooled exhaust that leaves salt vapors drifting in the exhaust manifold every time it is shut down. Sometimes the exhaust, due to improper design, may actually flood the engine with salt water. And these are only some of the poor working conditions faced by marine engines.A preventive maintenance tool
With a car engine, the manufacturer can draw up a table of scheduled maintenance and know that if this is adhered to, and the correct oil is used at oil changes, the engine will live up to expectations. Regular oil analysis would simply add another maintenance overhead without much benefit. However, with a boat engine the operating conditions are much harsher to begin with, the usage is more varied, and there is a far greater potential for the unexpected. Breakdowns, when they occur, are costlier to fix. The economics of operation are radically different. There is, in addition, an unquantifiable safety aspect: an engine failure in a car is an inconvenience; in a boat it could be dangerous. For all these reasons, oil analysis becomes a cost-effective, preventive maintenance tool. Let’s see how it works.
An oil analysis is done on a small sample of an engine’s (and sometimes also a transmission’s) crankcase oil. This sample is normally taken when the oil is being changed at the scheduled maintenance interval. It is mailed to a laboratory and subjected to a number of tests which will vary from lab to lab but should include most of the following:
1. Physical tests for the presence of water, antifreeze and fuel
2. Infrared analysis to determine soot levels, oxidation, and sulfur content
3. Spectrophotometric analysis to isolate various metals (including copper, iron, chromium, aluminum, and lead) and other contaminants such as silicon, sodium, and molybdenum.
An accompanying illustration shows a copy of a detailed test report from a first-rate laboratory. It shows what kinds of things may be included in an analysis, and how they are reported. It is worth exploring the significance of the various items on the report card.
· Water is measured as a percentage of the total weight of the sample. Traces of water, arising from condensation, are quite common, particularly in engines that are used infrequently, and for short periods of time (many sailboat engines). Higher levels of water are almost always the result of some kind of a coolant leak or siphon action through a water-cooled exhaust. While a little water is often inevitable, all water tends to promote oxidation (see below), causes rust to form on sensitive surfaces, and impairs lubrication. As such, any is undesirable.
· Anti-freeze is also measured as a percentage by weight of the total weight of the sample. Anti-freeze will only be present if there is a leak from a freshwater cooling circuit. Ethylene glycol (the major component of most anti-freezes) not only causes oil to form a sludge that lowers its lubricating properties and plugs passages, but also plates out as a damaging varnish on bearings and cylinder walls. Once present, this varnish is very hard to remove. Any level of anti-freeze is unacceptable.
· Fuel dilution is measured as a percentage of the oil sample by volume. Fuel leaks into the oil are more likely on diesel engines with internal fuel lines (not common on small diesels), but can also arise as a result of improper fuel injection and combustion, or engine damage (such as a holed piston crown). Fuel lowers the viscosity of the oil, lessening its lubricating properties and perhaps lowering oil pressure. Bearing failure and engine seizure are more likely with fuel dilution. If present in sufficient quantities in a hot engine, fuel vapors can lead to a crankcase explosion.
· Soot is reported as a percentage of the limit. Deriving this, and other limits, is a complex matter on which I will have more to say later. Soot is an undesirable, though inevitable, by-product of combustion. While much of it is blown out of the exhaust, some finds its way past the piston rings into the crankcase where it is picked up by the oil. Since it is insoluble, it slowly thickens the oil, reducing the oil’s lubricating properties, plugging filters, and in extreme cases forming a sludge that can completely plug slow-moving oil galleries, leading to a major engine failure. Diesels produce more soot than gasoline engines, and, as a result, use oils that are specially formulated to hold soot in suspension (detergent oils). Nevertheless, at some point the oil’s carrying-capacity will be exceeded; the less efficient the combustion process, and the poorer the quality of the fuel, the sooner this will occur. Soot is therefore, among other things, a useful measure of combustion efficiency.
· Oxidation, too, is reported as a percentage of the allowable limit. It is a natural consequence of both oil age and service that results from a reaction between oil and oxygen in the air. The rate of oxidation is increased with improper engine operation and by various contaminants (such as water). Oxidation increases viscosity and sludge formation with a corresponding loss of lubrication, and an increase in piston ring and piston deposits.
· Sulfur is another contaminant reported as a percentage of the allowable limit. It is found as a trace element in most diesel fuels. Some of it finds its way into the oil where it combines with moisture to form highly-corrosive sulfuric acid. Sulfuric acid is destructive to all engine parts. It can be particularly damaging when engines are laid up for extended periods (many sailboats, once again). Oils are formulated with special neutralizing agents to combat acid build-up, but over time these become depleted. The best way to remove sulfuric acid is to replace the oil regularly.
· Silicon and sodium, and the various metals, are described in terms of parts-per-million in the oil sample. Silicon and sodium have sources external to the engine, but metals are all internal. Silicon comes from dirt or dust in the inlet airandmdash;high levels indicate a plugged or ruptured air filter (or perhaps none at all) or air leaks in the inlet ducting and manifold. Silicon in oil acts much like a grinding compound, accelerating wear on all moving parts. Sodium might come from a cooling system leak (it is used as an inhibitor in some anti-freezes)andsbquo; but in a pleasure boat is just as likely to be from salt water finding its way into the engine, either by backing up a water-cooled exhaust or from excessive amounts of salt spray in the inlet air.
The various metals are produced by engine wear. Some wear is clearly inevitable, but rising metal levels point to accelerated rates of wear. The particular metal (or metals) involved can often aid in pinpointing the specific location of a problem long before other indicators sound the alarm. Lead, for example, is only found in bearings and bushings; iron is generally restricted to gears, shafts, cylinders and valve trains; and so on.Interpreting the results
Intuitively one senses that the kind of report shown here can be used to provide a very comprehensive picture of what is going on inside an engine. From this it should be possible to determine what steps, if any, need to be taken to keep the engine running at optimum performance. However, the problem for the lay person lies in knowing how to interpret the figures. For example, look at the 6/4/91 test data, what does 112 ppm of copper (Cu) signify? Is this normal or is it over a threshold limit? Is the engine okay, or is it time to press the panic button? Without some sense of the significance of the figures, much of the report is essentially meaningless.
Unfortunately, when it comes to making sense of these reports there are only one or two fixed absolutes (e.g., any level of anti-freeze is unacceptable). Interpreting the rest of the data is a matter of judgment and, just to complicate matters, this interpretation is going to vary from engine to engine and application to application.
Take, for example, the various figures for metals. Engine manufacturers conduct exhaustive tests to determine typical wear rates for bearings and other engine parts, and from these derive anticipated levels of metals in the oil. But these andquot;wear rateandquot; tables are not cast in stone; they evolve over time, changing with modified engine designs and components, and on the basis of feedback from the field. The wear tables themselves are the proprietary information of the engine manufacturer and may only be made available to in-house or licensed laboratories.
Allowable limits evolve in a similar fashion, and will be affected by changing fuel and oil chemistry, and increasingly by government intervention in the form of environmental regulations (emission controls). All figures will be affected by the age of an engine (its number of operating hours), its operating conditions, and other factors such as the quality of fuel available (the diesel sold in some Caribbean countries has a much higher sulfur content than that sold in the U.S.).
The technicians involved with a large manufacturer’s oil-testing program (such as Caterpillar) have access to a tremendous bank of knowledge and expert back-up. When the results of a specific analysis are plugged into this data bank, quite specific conclusions can be drawn about the state of the engine, what kinds of problems are developing, and what remedial actions, if any, need to be taken. All of this information is then recorded in the technician’s notes.
However, since few manufacturers of auxiliary sailboat engines have accumulated such a data base, and even fewer have integrated the data into a comprehensive oil sampling program, the average marine user of oil analysis becomes dependent to a considerable extent on the data base built up by a particular laboratory, and on the interpretative skills of the operator performing the analysis and making the report.
Some labs have more experience with one type of engine or application than another; some do a more detailed analysis than others; some simply report the test results while others give an interpretation; most will have a data base that is derived from just one geographic region. Choosing a suitable lab – one having experience with a particular engine and application, adequate testing procedures, meaningful test reports, and a willingness to answer follow-up questionsandmdash;may take some inquiries and experimentation.
The report shown comes from Southworth-Milton, Inc., a large Maine-based Caterpillar dealer that has an oil analysis lab in New Hampshire. This company not only has extensive experience in the marine and trucking industries in the northeast, but also some worldwide connections. The lab also regularly deals with a number of marinas and has accumulated considerable information on most of the marine engines found in pleasure craft. It is an example of a lab that would be an excellent choice for a mariner in the northeast, and, in fact, probably for mariners elsewhere, although it would not have the same depth of experience on engines which have been used outside its regional base.Regular sampling important
No matter how good the lab, there are only limited benefits to a one-off oil analysis. Some things may be picked up immediately, such as the presence of anti-freeze or excessively high wear rates, but many of the subtle benefits of an oil analysis will be missed. For this, one needs to establish a trend, and that requires three or more consecutive samples.
With multiple samples it is possible to paint a normal background picture for a specific engine in a specific application. Now, changes in any figures will stick out like a sore thumb, demanding remedial action. Take the following real life situation (courtesy Caterpillar and their scheduled oil sampling program):Sample#Hourson oilCu*Fe*Cr*Al*Si*Pb*
1247112226182256213158223262125112143742491280261579*Parts per million
At oil sample no. 3, dirt (Si), aluminum (A1), lead (Pb), and iron (Fe) all rose significantly, indicating dirt entry into the oil that was accelerating engine wear. The oil and filter were changed but at sample no. 4 the levels were still high, with aluminum and lead rising dramatically. A failed rod bearing was found. Although the crankshaft was scored, it was possible to regrind and reuse it. The engine repairs were not cheap, but a far more serious engine failure was averted. Perhaps more important, investigation that probably would not otherwise have occurred revealed the source of the dirt as a contaminated oil supply vehicle; the problem was rectified.
But now let’s look at another set of real-life figures (courtesy Caterpillar once again):Sample#Hourson oilCuFeCrAlSiPb
In this case the engine operating hours on samples no. 2 and no. 3 were not recorded. All three results indicated similar levels of silicon and the various metals. The dirt was high, which explained the fact that some of the metals were on the high side, but the numbers were still apparently acceptable. However, when the lab checked the engine hours it found out that the second and third oil changes had been made at just 125 hours engine run time, which meant that the dirt and metals readings were in reality considerably higher than on the first sample. An inspection found a faulty air housing gasket that was repaired.
The last example shows that the value of oil sampling as a diagnostic tool is heavily dependent not only on regular sampling but also on the sampling procedure itself, including documentation. In this respect certain things are essential:
· The sampling bottle, pump and hose (which, on small engines, is generally inserted into the crankcase through the dipstick hole) must be perfectly sterile.
· The oil must be taken when the engine is hot (after the oil has been thoroughly mixed up) and must be drawn from the mid-crankcase level (so that an atypical sample is not obtained).
· The sample must be fully labeled and annotated with as much information as possible, including the total number of hours on the engine, the brand and the type of oil, the number of hours on the oil, how much oil has been added since the last oil change, and any maintenance that has been performed on the engine (since this may very well affect the level and type of contaminants found in the oil).
I hope I’ve made the case for regular oil sampling. If so, there’s just one question left to answer: given the lack of advertising on the part of oil analysis laboratories, how does one get into a program and what does it cost? There’s really nothing to it. Southworth-Milton, for example, sells a starter kit for $150. This includes a sampling pump, sampling hose, ten sample bottles, and report cards all in a carrying case. The price includes the cost of processing the samples (it works out to $15 a sample). A refill kit (another ten sample bottles, plus report cards and processing fee) costs $110andmdash;$11 a sample. Other labs offer a similar service.
Since most pleasure boats only need an oil analysis once a season, few people will want to buy a multiple sample kit. But a number of boaters could invest collectively, or persuade the local marina (if it is not already providing an oil analysis service) to get into the business. For a few minutes work at oil change time, the oil analysis will likely reveal more about the health of the engine then any mechanic could discover in several hours.
If oil sampling is done properly and regularly it will enable a boat owner to gain a detailed picture of the health of his or her engine. If problems begin to develop, the analysis will frequently show them long before other indicators (smoke, knocks, loss of power, etc.) make them evident. If the analysis is acted upon long-term maintenance bills will be reduced, engine life extended, and boating made more reliable and safer. That’s a pretty good return on the $10 to $15 cost of the analysis!
Contributing editor Nigel Calder’s latest book is The Cruising Guide to the NW Caribbean, published by International Marine Publishing.Southworth-Milton Inc.,Wear Analysis Laboratory,Exit 6, Interstate 89,Hopkinton, NH 03229(603) 746-8631