Interpreting Your Engine Oil Analysis
Why Analyze Engine Oil?
Any sophisticated heavy-truck maintenance program includes regular engine oil analyses, which reveal early-warning signs of equipment problems, or, often, the need to simply change the oil. Unexpected equipment failures are costly, and having a documented data history also boosts eventual equipment resale value.
Where and How Often?
Engine oil analyses are performed by qualified laboratories, such as Acculube's. The cost depends on the level of analysis needed. For heavy-duty diesel engines, we recommend focusing on contaminants and trace metals, the condition of the oil's additives, viscosity, base number and other important information. Test results will also indicate if oil is excessively contaminated with fuel, water or antifreeze, all of which hinder oil's ability to lubricate.
The optimum frequency for oil analysis depends on the application, and guidelines are available from OEMs and other sources. Frequency may also be dictated by the results of the last analysis.
Sampling Your Oil for Analysis
Experts recommend that oil sampled for analysis be extracted from the same point, and modern trucks have a sample port for this purpose. The sample should be drawn while the engine is idling at operating temperature. Also, it is important that sampling be done consistently each time for uniformity of results. You can do this part yourself with the purchase of a simple pump, valves and tubing to extract the sample from the engine.
Reading the Results
The laboratory who performs the oil analysis will prepare a report listing its findings. Interpreting these findings in a relevant way is important, and some lubricant manufacturers and laboratories offer training in both oil sampling and report interpretation. At their most basic, lab reports have a space where recommendations are made based on the analytical results. Test results relating to viscosity, contaminants, wear metals and additives are indicated. Each of these is given a rating of normal, abnormal or critical. Normal means that the parameters checked are within reasonable limits and the next analysis can be done at a routine interval. Abnormal means that some parameters are outside the manufacturer's recommended limits. This may indicate another analysis should be arranged to verify the first results. Critical indicates immediate remedial action is needed.