The Basics Of Oil Analysis For Equipment Maintenance

oil analysis for equipment maintenanceOil is the most common lubricant around, mainly because it is easily available at a low cost and it does such a good job at slowing wear and tear from friction. It is no surprise that oil analysis plays an important role in equipment maintenance.

How does the oil analysis process work, and when should it be applied? We’ll tell you everything you need to know about how and why to make oil analysis part of your regular maintenance regimen.

What is oil analysis?

Oil analysis is an important part of “tribology,” the study of wear in machinery. Oil analysis uses various tools and techniques to reveal the properties of lubricating oil. This is important because the oil condition reflects the condition of the machine. In other words, it is like a blood test for your machinery.

oil sample analysis

Some results of performing oil analysis include:

  • lower maintenance costs
  • improved reliability
  • prolonged useful life of bearings, gearboxes, and other rotating equipment 

Because of these benefits, fleet managers, in particular, have a strong incentive to perform frequent engine oil analyses.

There are many different types of tests that will evaluate a variety of oil characteristics, each providing its own insight into the health of the equipment. Here are some of the most common routine tests.


Viscosity is the most important characteristic of a lubricant. 

A viscosity reading too high or too low can be the symptom – or the cause – of a variety of problems. It can be the result of using an incorrect lubricant or contamination from antifreeze or other solvent. Changes in viscosity can lead to problems such as oxidation or thermal stressors.

Elemental analysis

Particles larger than 5 microns are difficult to detect by spectroscopy. 

Analytical ferrography can identify particles and solid contaminants in lubricating oil without any particle size limitations.


Particles larger than 5 microns are difficult to detect by spectroscopy. Analytical ferrography can be used to examine wear particles and solid contaminants in lubricating oil without any particle size limitations.


FTIR or “fourier transform infrared” is another efficient way to test for several contaminants such as fuel, water, and soot using infrared technology.

Acid number and base number

The acid number (AN) test is an estimate of the amount of additive depletion, acidic contamination, and oxidation. 

Similarly, the base number is used specifically for combustion engines and represents the ability of the oil to neutralize acids that occur as a result of combustion and oil degradation.

Checklist for Creating a Preventive Maintenance Plan

Following a consistent Preventive Maintenance Plan can make life easier. Use this checklist to create your own!

Why perform oil analysis? 

Oil analysis helps you understand the conditions of the machinery you are testing. It reveals important information without the need to cut open or disassemble the machine. 

In this way, oil analysis is similar to other forms of non-destructive testing (NDT). It provides useful information on the condition of the machine without having to damage the machine in the process. 

From it, you gather enough information to perform corrective maintenance that eliminates potential problems. 

Here are some benefits that regular oil analysis can bring.

  • Maximizes oil service life
  • Extends equipment life
  • Prevents problems and breakdowns
  • Improves asset reliability
  • Increases asset resale value

Selecting a lab to perform oil analysis

Oil analysis requires specialized equipment and qualified professionals. Unless you have the budget to build an in-house lab or call in a mobile laboratory — and most of us don’t — you will be working with a specialized off-site laboratory run by trained oil analysis professionals. 

The International Council for Machinery Lubrication (ICML) is a widely recognized non-profit organization that regulates everything related to machine lubrication. ICML conducts certification exams and accredits lubrication professionals across the globe. 

Oil analysis certifications issued by ICML adhere to the International Organization of Standards (ISO) guidelines and include:

  • Machine Lubricant Analyst (Level I, II, III)
  • Machinery Lubrication Technician (Level I, II)
  • Laboratory Lubricant Analyst (Level I, II)
  • Machinery Lubrication Engineer

Another body that trains and issues certification to lubrication professionals is the Society of Tribologists and Lubrication Engineers (STLE). They issue two certifications concerning oil analysis:

  • Certified Lubrication Specialist (CLS)
  • Oil Monitoring Analyst (Level I, II)

STLE has its own set of standards and procedures to certify oil analysis professionals and analysts.

Oil analysis process

To ensure the oil analysis results you receive are accurate and useful, it is essential that you follow some key steps in the process of collecting and sending your oil sample to the lab. 

Sample collecting

The sample needs to be representative of the oil flowing through the machine. The three things to keep in mind while taking oil samples are:

  • ensuring maximum data density  
  • minimizing disturbance or potential contamination of the sample
  • setting the right sampling frequency to develop relevant trends

Common techniques are drop tube sampling, pressurized line sampling, and drain port sampling. 

Oil samples have to be taken in clean containers using equipment like a vacuum suction pump or another device. The equipment you need will often come as part of an oil analysis test kit provided by the lab. 

oil sampling kit

An example of an oil sampling test kit (Image source)

The ideal oil sample is the one taken while the machine is in operation. However, that is not always the safest or most straightforward thing to do. 

In these cases, collect the sample right after the engine is turned off. If the lubricating oil is allowed to rest, any sediments or contaminants  will separate and potentially ruin the accuracy of the sample.

Here is an in-depth guide on how to take an oil sample for additional information.

Sending the sample for lab testing

If you are outsourcing the oil analysis, which is likely, the lab you are working with will provide you with an oil analysis kit that includes the appropriate labels and directions for shipping it to the lab. Follow the instructions, then wait until the results arrive. In most cases, you will have results within days.

Upon receipt of your sample, the lab will perform tests based on the situation. 

Routine oil analysis

Routine tests will repeat the same battery of test for comparison over time. Changes in results are monitored and investigated to determine potential causes and actions that may need to be taken. 

Ad hoc or unscheduled analysis

The type of tests completed in this scenario are based on the following considerations: 

  • the failure modes of the machine being monitored
  • the circumstances of the incident triggering the analysis
  • the triggers/findings sought in order to trigger an appropriate response plan

An application-specific approach (separate tests for each machine) or a single test package for all assets are both viable options. Your lab will help you identify which method is appropriate for your needs. 

The Essential Guide to CMMS

The Essential Guide to CMMS

Reading and using your oil analysis report

Oil analysis reports do not give cut-and-dry recommendations. 

Instead, you will receive a report of the different ratings and chemical levels in your oil after your oil test

Whether or not those levels are good or bad depends on the ideal oil parameters for each machine you have tested. Make sure you have consulted the manuals provided by the OEM to establish ideal levels and baselines to help you interpret your report. 

oil sample analysis report example

Oil sample analysis report (Image source)

We discussed the different types of tests in an oil analysis above, but here are the three most common tests, and what their findings may mean:

  • Viscosity: Excessive oil viscosity dampens machine performance. As contaminants and elements in the machine increase, the viscosity of lubricating oil increases accordingly.
  • Elements: Spectral analysis or ferrography helps determine whether the present elements are contaminants or part of normal wear and tear. According to the number and quantity of materials present, expert oil analysts can provide specific maintenance recommendations.
  • Acid number: A high acid number indicates a high chance of corrosion. The acid number should be kept within the range advocated by the OEMs.

Implementing machine maintenance in response to findings

The real value of oil analysis lies in the maintenance actions taken in response to its findings. Common recommendations include oil filtration, oil changes, or further monitoring. 

As with any other condition monitoring method, you should prioritize corrective maintenance is based on the criticality of the asset, the impact of equipment failure, and the cost of machine downtime. 

If your oil analysis report suggests a big capital expenditure, more tests must be done to confirm the need.

To truly address issues identified in your fluid analysis and ensure its effectiveness, it is best to leverage a CMMS software. CMMS’s streamline the oil analysis process by logging test results over time, triggering and assigning corrective actions and preventive maintenance work, and measuring their effectiveness.   

Performing repeat oil analyses over time

A single oil sample report doesn’t do much on its own. 

Performing oil sample analysis at consistent intervals using the same test package compounds your return on investment. 

It is the comparison of one test with another that provides the most value. The changing characteristics found in oil analysis reports indicate where your equipment maintenance resources are best spent. 

Experienced oil analysts can find the causal factors affecting changes in oil analysis reports while plotting and tracking trends.

A blood test for machines

Conducting an oil analysis at regular intervals gives insights into machine reliability and remaining useful life. These insights can be used to efficiently manage maintenance resources and extend the lifetime of engines and other machines.

If oil analysis is a blood test for a machine, a good CMMS is like its personal health record. It is a repository for all the useful information you need to keep your machines healthy for a long time. 

To learn more about how a CMMS like Limble can support every part of your maintenance strategy, schedule a demo or start a free trial.

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