The various numbers in an oil analysis report offer valuable information about the mechanical health of your excavator, backhoe or other machines.
“They provide insight into the performance of the oil as well as the internal condition of your equipment,” says Ed Kellerman, manager of Oil Analyzers Inc., an independent testing lab operated by Amsoil Inc. However, he admits, the numbers by themselves might be confusing.
If you underst how the report information is derived and what the numbers measure, that can help you avoid confusion — and improve your ability to spot and fix any minor problems before they become major ones.
The reporting process
A number of labs around the country analyze oils from engines, transmissions, hydraulic systems and differentials. Kellerman recommends using ISO-certified labs whose analysts are certified by a recognized organization like the Society of Tribologists and Lubri-cation Engineers (STLE).
In addition to information about the customer, the machine, the type of oil and when the sample was tested, a typical analysis report lists the types of tests conducted and the results. It also explains any unusual readings and recommends appropriate steps to take in response.
For example, the routine analysis performed by Oil Analyzers evaluates both the physical and chemical properties of the oil using several tests. The report compares the actual test measurements for each property and compares them to average or normal values, which are based on recommended oil drain intervals.
Readings that fall outside the normal range are highlighted by a code: “A” for abnormal or “C” for critical. “An ‘A’ indicates cause for concern but requires no immediate steps to fix the problem,” Kellerman explains. “However, a ‘C’ reading calls for prompt corrective action to prevent catastrophic failure of the machine. In that case, we call or fax the customer about the problem.” The report includes recommended actions to take for each “A” or “C” reading, such as changing the air filter or replacing a gasket.
Chemical properties
One key component of the company’s testing process is spectrochemical analysis, done with an inductive coupled plasma (ICP) spectrometer, which detects metal particles in the oil that are smaller than 6 microns. This instrument identifies the type of metal and measures its concentration in parts per million. Some particles are generated by wear of bearings, gears and other components. Some particles are from dirt or other contaminants in the oil. Others are from metals added to the oil by the manufacturer.
In the case of engine oil, the Oil Analyzers’ tests can detect 12 different metal oil additives, such as boron, magnesium and zinc, and eight types of wear metals, including copper, lead and tin. The presence of metals and other particles can indicate problems. For example, silicon might indicate that dirt is getting into the system through a leaking seal. A high chromium reading could mean excessive wear of piston rings, while an unusual aluminum level could signal the need to check the condition of a torque converter.
“No two pieces of equipment wear at the same rate,” says Kellerman. “Many factors, like age of the machine or how it’s operated, can affect the amount of wear metals in the oil.”
Get the Most from Oil Analysis
As good as an oil analysis is in spotting maintenance problems, a whole series of these evaluations is even better, reports Darryn Wallace, a senior technical service specialist with Oil Analyzers Inc.
“An analysis shows the machine’s condition at one point in time,” he says. “You need to test the oil on a consistent basis to establish trends in the types of wear and the rate at which it is occurring. You can then base maintenance practices on these trends.
“For example, if, after testing several samples over time, there are no drastic spikes or drops in any key measurements, you may be able to extend the time between oil and filter changes to save time and money. Or, the trend in test values may show that you need to shorten these intervals to prevent problems. Also, by knowing more precisely when the oil needs to be drained and the condition of your equipment, you can schedule this or other maintenance when it’s convenient for you.”
To establish a good baseline for tracking trends, Wallace recommends testing the oil within the first few hours of operating a new machine or after changing the type or brand of oil. The next two samples should also be evaluated after fairly short intervals. “Once trends in the measurements start to develop, you can then figure out a more reasonable interval between tests,” he says.
Finally, Wallace notes, specific testing methods can vary from one lab to another. That’s why he suggests sticking with one good lab to get a more accurate picture of equipment condition and maintenance needs over time.
Physical properties
The other major part of the testing evaluates any changes in the physical qualities of the oil. “These changes can have a dramatic effect on the oil’s ability to protect the component from wear or failure,” Kellerman says.
Viscosity. A buildup of certain contaminants can affect the oil’s viscosity. Using a viscometer, analysts measure the time it takes for the oil to flow down one side of a U-shaped tube and up the other. Some types of contaminants will thicken the oil, slowing the flow through the tube. Others will thin the oil, speeding up the flow.
Water/antifreeze contamination. A crackle test (a drop of oil placed on a hot plate sizzles or cracks if it contains moisture) is used to test for water contamination. Water in the oil can indicate such problems as condensation, a leaking radiator or transmission oil cooler, defective seals, or a blown head gasket. A chemical test can reveal the presence of glycol and coolant additives, which can corrode engine components and destroy the oil’s ability to lubricate.
Fuel dilution. Several tests can be used to detect fuel in the oil. Fuel dilution can reflect several causes, including defective injectors, improper timing, and a leaking fuel pump or lines.
More contaminants. A Fourier Transform Infrared (FTIR) scan can identify several types of contaminants. They include:
• Soot, the result of incomplete combustion from such sources as defective injectors, clogged air filters and problems with intake/exhaust valve guides.
• Solids like dust, gasket material and debris left during the manufacture of components.
• Oxidation of the oil, caused by high operating temperatures or over-extended oil change intervals, which can cause corrosion, increase viscosity and deplete additives.
The FTIR scan can also reveal any abnormal nitration, the result of excessive blow-by, which can increase oil viscosity, cause corrosion and lead to increased wear and poor engine performance.
Total base number (TBN). Engine oils contain base (alkaline) additives to neutralize the acidic by-products of combustion. The oil’s ability to neutralize these acids and protect the engine from corrosion is measured by its TBN value. The higher this number, the greater the protection.
“Because oil loses its ability to neutralize acids over its service life, measuring the TBN strength of the oil is very important when extending oil drain intervals,” Kellerman says. For non-crankcase lubricants, he adds, measuring the Total Acid Number (TAN) provides a good indication of a lubricant’s condition.
If you don’t perform oil analysis on your equipment now, maybe you should. If you do, it makes sense to understand the meaning of the tests you’re paying for. More information is available at www.oaitesting.com.
Greg Northcutt is a freelance writer based in Port Orchard, Wash. He can be reached by e-mailing this publication at editor@onsiteinstaller.com.
