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7 January 2017

Used oil analysis (UOA) can provide critical information regarding the condition of the oil being analyzed and the machine or compartment from which it was drawn. However, reading a UOA report can be a daunting task for those who are unfamiliar with the process.

Please note that it is not the aim of this article to discuss the interpretation of the data presented in an UOA report; rather the goal is to provide a logical and sequential process of reading through the report. A discussion on oil analysis interpretation will be the subject of an upcoming Engineering Solutions article in a future edition of HD Focus.

Starting from the top of a Castrol® Labcheck UOA report (see report example below):


Review the Unit Information:

Worksite, Unit ID, Compartment, Unit Age

You may be receiving results for more than one location. If so, you can determine which worksite the sample is from, as well as whether the specific Unit, Compartment, and Compartment Age have been identified properly.

Review Sample Information:

Ensure that the Sample Date, Lube Age and Lube Maintenance activities are accurately reported

Note that the lack of complete and accurate information is the most common issue affecting the successful implementation of a UOA program. The old saying of “garbage in equals garbage out” is never more applicable than with used oil analysis. The lab can only provide good-quality results if it is initially supplied with good-quality data.

Review Results:

Review Acceptable (A code) or Unacceptable (B, C or D code) results

A Castrol Labcheck sample report can result in one of four possible letter codes: A, B, C or D. These codes are defined as:


A  Acceptable results; no further action is required
B  Slightly over or below acceptable levels
C  Notably over or below acceptable levels; advise monitoring
D  Severe level of wear or contamination; requires immediate action to correct


If the sample is Acceptable, you may still want to review the specific results in order to appreciate what normal results look like for specific types of components. If the sample is Unacceptable, you should review the report looking for the specific test results that are flagged such as Wear, Dirt (Silicon), Viscosity, Coolant, Fuel, Oxidation, Nitration, Base Number or Acid Number, and Soot.

If the sample is flagged for Wear, look for the presence of Dirt (Silicon), Water, or other contaminants to understand what may be the cause.

If Viscosity is flagged, consider the reported conditions or contaminants that may be responsible. Look for accompanying flags for Fuel Dilution, which is usually associated with lowered viscosity, or Soot, which is usually associated with higher viscosity. Be aware that Viscosity is often flagged because incorrect information is provided on the sample label. Measured viscosity results are compared to the lubricant information on the sample label. If there is a mismatch between what was measured and what was provided on the label, the result will be flagged as out of range. If viscosity is flagged, always review the “Oil Type” at the top of the report and compare that to what was measured and reported.

Along with Dirt, Glycol and Fuel are the most serious types of Unacceptable results. Any of these conditions that are left unchecked can lead to catastrophic damage in a very short period of time. Conditions that lead to low levels of contamination can worsen quickly, leading to high levels of contamination, which can lead to component failure. Flags for any of these conditions need to be acted on quickly. Resampling to confirm results and use of other diagnostic tools should be employed to avoid component failure.

Review Lab Comments:

All detected conditions, suggested actions, and cautions are issued in this section

Review History & Trends:

One sample can provide helpful information, but trends are much more meaningful

Look for trends in the sample history that may help to determine the significance of the results. In all aspects of UOA, accuracy and consistency are critical and provide the most trustworthy results.


Remember not to make important repair decisions based solely on the results of just one oil sample. Always resample to confirm Unacceptable results before taking action. Be sure to consult members of your maintenance team and consider using other diagnostic tools and practices that are available to confirm suspected faults.

Oil analysis is the most highly recognized proactive maintenance tool in the industry. When used properly, UOA can provide a user with insight about the condition of a fleet and the effectiveness of maintenance practices. Knowing how to properly read a report and extract meaningful and useful information from all of the data is paramount. With time and practice, you can develop the skills needed to efficiently read a UOA report to effectively use it to help you maximize the benefits of your used oil analysis program.

As always, please contact your Castrol sales or field engineering representative for assistance.