Benefits of oil analysis
A detailed analysis of engine, transmission and hydraulic oils enables you to identify potential problems before a major repair is necessary. Oil analysis also may help you reduce the frequency of oil changes and increase the resale value of your used equipment.
What is oil analysis? Oil analysis involves sampling and analyzing oil for various properties and materials that indicate wear and contamination in an engine, transmission or hydraulic system. Sampling and analyzing on a regular basis establishes a baseline of normal wear and can indicate when abnormal wear or contamination occurs.
An oil analysis tells you a lot about how the equipment was used and what condition it's in. Oil that has been inside any moving mechanical apparatus for some time reflects the exact condition of that assembly. As moving parts make contact, wear occurs and introduces minute metal particles to the oil. These particles are so small that they remain in suspension. Many products of the combustion process also become trapped in the circulating oil. In addition, the oil may be exposed to external contamination. Identifying and measuring these impurities indicates the rate of wear and level of contamination. Thus, the oil becomes a working history of the machine. An oil analysis also suggests methods to reduce accelerated wear and contamination.
A typical oil analysis can indicate the presence of contaminants and tell you if you've been using the appropriate lubricants. Oil analysis detects: * Fuel dilution of lubrication oil * Dirt contamination in the oil * Antifreeze in the oil * Excessive bearing wear * Misapplication of lubricants.
Some wear is normal. However, abnormal levels of a particular material can give an early warning of impending problems, prevent a breakdown and allow for corrective action such as repairing an air-intake leak before major damage occurs. One major advantage of an oil-analysis program is being able to anticipate problems and schedule repair work to avoid downtime during a critical time of use. Early detection can: * Reduce repair bills * Reduce catastrophic failures * Increase machinery life * Reduce non-scheduled downtime.
Evaluating used equipment A complete record of oil analyses you've performed can prove to be a great tool when selling a piece of used equipment. It shows the potential buyers how you have maintained the equipment as well as any adjustments you made to it during its life. The history also is a good indicator of potential future repairs and overhaul requirements.
When buying a piece of used equipment yourself, you also can take advantage of the benefits an oil analysis can offer. However, without knowing the amount of operation of the oil being analyzed, you should consider the test conclusive only if it indicates a problem. A good report could result from either no problems or a short length of service of the oil.
Physical and metal tests During a complete oil analysis, you should test the sample for both physical properties and metals. Some of the physical properties tested for and usually included in an oil analysis: * Antifreeze. This forms a gummy substance that may reduce oil flow. It leads to high oxidation, oil thickening, high acidity and engine failure if not corrected. * Fuel dilution. This property shows that oil has thinned, lowering lubricating ability and potentially causing a drop in oil pressure. This usually causes higher wear. * Oxidation. Checking for oxidation is a measure of gums, varnishes and oxidation products. High oxidation from oil that became too hot or was used too long can leave sludge and varnish deposits and thicken the oil. * Total base number. This generally indicates the acid-neutralizing capacity still in the lubricant. * Total solids. These include ash, carbon, lead salts from gasoline engines and oil oxidation. * Viscosity. Viscosity is a measure of an oil's resistance to flow. Oil may thin due to shear in multiviscosity oils or by dilution with fuel. Oil may thicken from oxidation if it is run too long or too hot. Oil also may thicken from contamination by antifreeze, sugar and other materials. Following are some of the metals for which oil is tested and some of their potential sources: * Aluminum. Thrust washers, bearings and pistons are made of this metal. High readings can be from piston-skirt scuffing, excessive ring-groove wear and broken thrust washers, among other problems. * Boron, magnesium, calcium, barium, phosphorous and zinc. These metals normally are from the lubricating oil additive package. They include detergents, dispersants and extreme-pressure additives. * Chromium. You typically associate chromium with piston rings. Dirt coming through the air intake or broken rings can cause high levels. * Copper and tin. These metals normally come 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 normally will be high during break-in but will decline in a few hundred hours. * Iron. This can come from many places in the engine, such as liners, camshafts, crankshaft, valve train and timing gears. * Lead. Lead is associated with bearing wear, but fuel source (leaded gasoline) and sampling contamination (use of galvanized containers for sampling) are critical factors in interpreting this metal. * Silicon. High readings generally indicate dirt or fine sand contamination from a leaking air intake system, which cause excessive wear from abrasion. * Sodium. You normally would associate high readings of this metal with a coolant leak. But they also can be from an oil additive package.
Taking an oil sample It is important to take an oil sample that is representative of all the oil in the machine. Always be sure the oil is hot and thoroughly mixed before sampling. Handle hot drained oil with care--it could cause serious burns.
The easiest time to obtain a sample may be when the oil is being drained for an oil change. Sampling at this time usually involves letting some of the oil drain and then catching a sample in an appropriate container.
You also can obtain samples without draining oil by suctioning oil out through plastic tubing routed down into the oil reservoir. In any case, it is important to have an appropriate container and follow sampling directions thoroughly. A lot of testing laboratories will provide you with a kit that includes a sample bottle. Many of the tests are for measuring materials on a parts-per-million basis. So, the container must be sterile or the test may pick up contaminants what was in the container before.
Cost and convenience Cost of oil analysis will vary according to the laboratory and extent of the analysis. Typical charges are $10 to $30 per analysis. You can justify the expense of the analysis if it alerts you to a major problem that you can correct in the off-season and prevents downtime when you need the machine.
Several companies have developed oil-analysis kits that make oil analysis convenient. These kits include the sample bottles, suction pump and tubing, and sometimes a pre-addressed, postage-paid mailing container.
Locating a source Your local fuel and oil supplier or machinery dealer may be the most convenient and economical source for oil analysis. However, not all fuel and oil suppliers or machinery dealers conduct oil-analysis tests. Independent laboratories are another course. You can locate them in the Yellow Pages under the classification of "Laboratories."
Results Typically, you will receive the results of the laboratory analysis 2 to 4 days after the lab receives the sample. The laboratory may note when the analysis shows an abnormal condition and issue a caution or recommendation accordingly. Typical recommendations might be: Example 1: Bearing metals indicate wear. Inspect all bearing areas for wear. Resample at half interval. Example 2: Unit is in satisfactory condition. Resample at normal interval. Example 3: Abrasion indicated. Inspect air-filtration system. Upper cylinder wear indicated. Excessive fuel dilution. Resample at half interval.
Optimum maintenance interval Most maintenance experts realize that the "average need" usually determines the oil-change intervals for both engines and transmissions. No two pieces of equipment have the same preventive maintenance needs. Each machine has different imperfections and operates under different conditions. Operators performing smaller or lighter jobs can cause different conditions on engine and transmission wear than those that occur during more extended use. When using oil analysis to determine maintenance intervals, little guesswork exists. Records show that some equipment can run safely two or three times longer than recommended intervals. The oil analysis may show that you are changing the oil more often than necessary—or not often enough.
By eliminating too-frequent oil changes, you reduce the cost for oil and servicing, and also reduce the amount of used oil with which you must deal. This is an important pollution-prevention method—reducing the source.
Robert Grisso is an extension engineer and Steven Melvin is an extension educator at the University of Nebraska-Lincoln.
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