Interpreting Heavy-duty Motor Oil Analysis Reports

Donnie Thweatt, Chevron Tom Bell, Chevron

Just as a blood test can deliver life-saving information, heavy-duty motor oil (HDMO) analysis is about keeping equipment in good health. A patient may look and feel fine but still have physical problems.

In the same way, you cannot see inside your equipment, and monitoring the fluid condition can help you determine how to keep it running longer and better.

Avoiding the financial impact of equipment failure is one benefit of oil analysis. Increased equipment performance and utilization also have a direct effect on profitability and productivity.

Maintenance costs are reduced when unexpected repairs are reduced. In addition, having documented reports on engine oil condition can enhance resale value.

With all of these reasons to perform regular oil testing, it is an essential part of a reliability program that is fine-tuned for business success.

For some large truck lines, for example, oil analysis is performed as a core part of the scheduled maintenance program. Based on engine class and make, oil analysis reports can be key to setting the interval for draining the engine crankcase and refilling with new oil.

While the drain interval recommendations of equipment manufacturers should be followed, some manufacturers require purchasers of their equipment to maintain fluid cleanliness to meet extended warranty guidelines.

Looking ahead, HDMO analysis is likely to become even more important and prevalent. Oil analysis will become essential for properly maintaining the new engine systems introduced to the market starting in 2007.

When engine technology changes, fleets already involved in used oil analysis will most likely increase the frequency of analysis to validate their existing practices or uncover the need for modifications.

The ability to interpret the results of HDMO analysis is vital to guiding significant decisions about preventive maintenance activities and drain intervals that can directly impact the bottom line. This article addresses the basics of oil sampling and interpreting the resulting reports.

Selecting an Oil Analysis Service

Oil analysis is performed by specialized laboratory services. It involves searching for the presence of wear metals, dirt, coolant additives, lubricant additive metals and viscosity as well as analyzing the acid-neutralizing capability of the oil itself.

The original equipment manufacturer (OEM) or oil supplier can recommend a qualified oil analysis laboratory. A best practice is to ask if the laboratory is certified and if it is audited on a regular basis. Another approach is to look at trade journals and find a laboratory located near your business. Confirm that it is certified by a standards organization such as ISO 9000 or ISO 17025.

Companies which provide laboratory services report costs ranging from $9 to $15 per sample, depending on the thoroughness of the analysis. There are two types of oil analysis reports: a basic report and a diesel crank case report.

The basic report provides the minimal amount of information focusing on wear metals and contaminants only. The diesel crank case reports provides feedback on wear metals, contaminants, additives, viscosity and base number (BN), which is critical in understanding extended drain intervals.

More extensive analyses use more chemicals and can also involve disposal of hazardous wastes, so they are slightly higher in price. It’s important to keep in mind that the money saved in preventive measures and productive machinery time will far outweigh the costs of a sample.

Performing Sampling

The frequency of sampling is often determined by the application, and the laboratory can provide detailed guidelines. OEM recommendations should be followed, but based on report results and the operating environment, a severity-based decision may be made to sample more frequently.

In taking the oil sample, a pressurized sample is taken from the main oil gallery, after the pump and before the oil filter. During sampling, the engine should be at idle at operating temperature. Most trucks today have a live sample port designed for this purpose.

A sampling service will perform sampling on-site, but you can also extract the sample and send it in for analysis. For this purpose, specialized pumps, tubing and sampling valves for specific applications can be purchased.

The laboratory will provide sampling bottles and forms (usually prelabeled and including return postage), and samples (basic test packages) are typically tested within 24 to 48 hours upon receipt of the sample at the laboratory.

Consistency in sample collection is critical to success. Using the same method for each sample removes variables, making comparisons more informative. If the temperature or operating condition deviates from what has been normal for past samples, it is important to note these changes on the form that accompanies the sample to the laboratory. This process will ensure that the comment is on the sample report.

In addition to noting any variations, it is important to provide the laboratory with other information to enable it to provide the most useful comments and recommendations possible. Engine model, hours/miles on the engine, pressure, hours of oil, date of last top-off, and oil name/grade are all vital data points to provide to the laboratory.

Interpreting Results

Once an oil analysis report is returned, it is important to review the information and interpret the data points. Based on the report, you can determine whether action is needed. The report does not pinpoint specific problems, but does provide a starting point for analysis.

Depending on which oil analysis lab or oil supplier performs the oil analysis, the information on the report will be organized differently. Many lubricant manufacturers and oil analysis laboratories offer training in oil sampling procedures and report interpretation.

There is always a suggestion box included in the report where the laboratory draws attention to specific results and offers broad suggestions and recommendations. Each test is clearly identified, and in general, the information is organized in a spreadsheet with numbers indicating results for viscosity, contaminants, wear metals and additives.

Viscosity is the property of the oil that resists flow and is the basis of an oil’s SAE grade.

Contaminants indicate contamination from outside the system like the soot that settles from fuel combustion, coolant presence, water and fuel. The report breaks down the specific contaminants and lists their possible sources outside the system and where wear may be occurring.

Wear metals are the debris/particles in the oil sample that indicate wear from surrounding parts. The report breaks down these elements and lists the possible source of each wear metal.

Additives are blended into the oil in different formulas and quantities by the manufacturer. The oil analysis report lists each element and its source.

For each category, there are three possible results: normal, abnormal and critical.

For contaminants, for example, “normal” indicates that oil contaminants are within expected parameters, and resampling can be done at the normal intervals. “Abnormal” indicates that some data points are outside of expected parameters, as compared to OEM wear tables.

“Abnormal” is an alert to pay attention and monitor, or to resample to ensure that the first results were accurate. “Critical” indicates a serious problem with the level of contaminants in the oil, and that immediate action should be taken.

Receiving Value from the Activity

To maximize the value from an analysis program, it is important to avoid three common mistakes:

Reacting based on a single sample — if you receive a “critical”, resample to ensure that the initial oil sample was correct.

Failing to use proper sampling procedures — proper procedure entails taking a pressurized sample from the main oil gallery with the engine idling at operating temperatures.

No reaction to the oil analysis report — the purpose of sampling is to provide thorough information to guide significant decisions about preventive maintenance activities and drain intervals. This “heads up” can directly impact your bottom line by leading to preventive actions to ensure equipment uptime.

Engine oil samples can provide the extra knowledge for you to find and fix problems early, before they cause serous problems. With an ongoing oil analysis program that enables you to use current and historical data to compare trends, you can maintain the life and value of your equipment more effectively.

Looking at historical data will also help you make more informed equipment purchases in the future. By evaluating equipment performance over time, you will know which models and manufacturers provide the best service under specific work conditions.

Ultimately, the purpose of systematic HDMO analysis is supporting business success. The cost of oil analysis is a small price to pay for advance warning that can prevent expensive and disastrous failures and downtime.

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