Used Oil Analysis – How It Can Help Maintain Your Equipment

Taking an oil sample from your equipment is like taking a blood sample. Just as a blood sample can show that your blood is ok and that your organs are working correctly or that there are potential problems, so too can an oil sample show the same for your oil and equipment.

Used oil analysis can tell you if the oil needs changing, help determine suitable oil change intervals and whether your engine, gearbox or transmission etc., are wearing normally or abnormally. It can also assist in determining why the oil and/or equipment aren’t performing as expected.

Benefits of Used Oil Analysis

There are many benefits of Used Oil Analysis

  • Reduce maintenance costs
  • Increased equipment availability
  • Improved safety e.g. aircraft
  • Extended oil drain intervals
  • Longer equipment life
  • Confidence in equipment reliability

Why should you pay for this when everything is running ok?

Regular oil testing is like an insurance policy as it gives you peace of mind and can warn you of any major problems before they happen. It can’t predict a major catastrophic failure but it can tell you when normal wear and tear is getting to the point where a service is required in order to possibly avoid the catastrophic failure.

There are two types of used oil analysis testing

The first is a once-off test. This is not very useful as there is no baseline to tell you if the results are good or bad, hence it is very difficult to give an interpretation of the condition of the oil based upon a single test value.

The second type is regular testing which can give you a trend, similar to when you check your cholesterol levels over time. The previous test results are important in determining whether major changes have taken place. This is often called progressive oil analysis.

Factors which effect oil during use

There are many factors which effect oil during use. 

  • Contact with air causes oxidation, which in turn can form corrosive acids, sludge, deposits and lacquer.
  • Temperature, if high will accelerate oxidation.
  • Very high temperatures can cause thermal cracking, i.e. break down of the oil, which then forms volatile compounds and deposits.
  • Mechanical action can also breakdown the oil.
  • Additive depletion, which we will explore in future articles.

Oils can also be contaminated during use by various means:

  • Wear, debris, dirt, dust, sand, paint, etc. can cause accelerated oxidation and sludge formation
  • Using a different oil make and/or viscosity grade, greases, and chemical coolants
  • Combustion products from the gasoline, gas or diesel engine itself
  • Cleaning agents not completely removed after an equipment strip down and rebuild

How to Take Oil Sample

Before we delve further into the individual tests which can be conducted on oil, it is very important to know how to take the oil sample in order to get the best results from your chosen laboratory.

For determining oil condition, take the sample after the equipment has been running for a while from the dipstick tube or from a drain plug, discarding the first quantity so that debris from around the plug doesn’t go into the sample bottle.

For determining the cause or origin of a sludge or deposit, take a sample of the sludge or deposit as well as the oil.

It is extremely important that these samples are representative. Provide as much information as possible to the laboratory, for example:

  • Oil make and grade
  • Kilometres or hours since last oil change
  • Oil drain frequency
  • Type of fuel used
  • Distances normally travelled e.g. short trips to shops or long trips across town.

Good Sample Bottle

It is also very important to have a good sample bottle. The sample bottle should preferably be transparent, so that the laboratory chemist can inspect the oil visually.

Most laboratories will provide the correct sample container and label. The bottle must be clean and close well.

For routine testing a bottle of approximately 100ml is usually supplied, so fill this to approximately 90% full to enable shaking by the laboratory.

You should provide all the necessary information on the sample label.

In my next article I will describe the various tests that can be performed, what they can tell you and how this can help you maintain your equipment.

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