The many elements of oil analysis

Heavy mobile equipment and plant is frequently exposed to severe environmental and working conditions, so regular maintenance is necessary. Taking a preventative approach to maintenance with an effective fluid and condition monitoring program will help to maximise the investment in your equipment, by reducing unexpected failures and costly unscheduled downtime.

Elemental analysis

Elemental analysis is an integral part of a fluid analysis program that helps producers maintain equipment performance and maximise availability.

Through regularly scheduled testing of oil samples from the engine, hydraulics, powertrain and other lubricated compartments, elemental analysis detects tiny metal particles caused by component wear.

Every oil-washed system – engines, hydraulics, transmissions and final drives – produce wear metals in everyday operation. If wear accelerates, the concentration of wear metal particles increases, signalling a problem.

Elemental analysis enables producers to find problems before they result in major repairs or machine failure. Elements typically identified through elemental analysis are aluminium, antimony, barium, boron, cadmium, calcium, chromium cobalt, copper, iron, lead, magnesium, manganese, molybdenum, nickel, phosphorus, potassium, silicon, silver sodium, sulphur, tin, titanium, vanadium and zinc.

Infrared analysis

Oxygen exposure, heat and contaminants cause all oils to degrade. Engine oil is particularly susceptible to degradation by sulphur, nitration, by-products of combustion, high temperatures and water from the combustion process or condensation.

Infrared analysis (also known as oil condition analysis) is part of the comprehensive oil analysis program undertaken at Hastings Deering. It helps prevent component damage by monitoring oil and keeping track of its degradation and combustion efficiency.

This analysis also allows producers to correct problems that affect oil performance.

The bottom-line benefit is maximum oil performance, optimum oil change intervals and reduced repair costs.

This testing process also provides information about the oil’s soot content, oxidation, nitration and sulphation.

Visual inspection

Oil samples can become contaminated with water in several ways. By-products from combustion, condensation and external ingress are the main mechanisms by which water can enter a compartment.

Water contamination reduces an oil’s effectiveness to lubricate and can rapidly cause damage to components.

Water testing performed at a Hastings Deering laboratory can be carried out in one of three ways. The first test involves dropping some sample onto a hotplate with a fixed temperature. This is a rough test but can quickly identify samples containing large amounts of water. The second type of testing is infrared analysis, where water is detected by changes occurring in the oil.

The third type of water testing offered by the laboratory is Karl Fischer testing. This test uses a titration method and can quantify water very accurately. This test is not included in Hastings Deering’s basic oil analysis kit and must be purchased as an additional test.


Oil samples, especially engine oils, can become contaminated with fuel during equipment operation.

Fuel contamination lowers the viscosity of the oil and degrades its ability to lubricate effectively. In addition, diesel fuel contains molecules that are pro-oxidants and can increase the amount of oxidation in an engine. Fuel contamination can also cause a premature loss of base number (loss of corrosion protection) and oxidative thickening of the oil, causing deposits and mild starvation.

The Hastings Deering laboratory uses gas chromatography to detect fuel dilution in engine oils and is accurate from two per cent to 10 per cent. Values greater than 10 per cent indicate a major problem, with imminent failure very likely.


The viscosity of a liquid is a measure of its internal friction or its readiness to flow. Various factors contribute to a fluid’s viscosity, and one of the main things that changes viscosity is temperature. The laboratory routinely analyses the viscosity of oil samples using an instrument that measures ‘kinematic viscosity’.

For most samples this involves reading the viscosity of the sample at a fixed temperature of 40°C. For engine samples, an additional reading is taken at 100°C to check the oil’s viscosity at an engine’s running temperature.

One of the major causes of viscosity problems in engines is fuel dilution. As fuel mixes with the oil, it reduces the overall kinematic viscosity of the oil, thereby compromising the oil’s ability to maintain adequate film thickness.


Particle count analysis

Counting the tiny particles in an oil sample identifies harmful contaminants that shorten component life. It can also pinpoint larger particles that signal imminent equipment failure.

This analysis identifies particles as small as four microns (μm) in size and will also identify particles greater than 50μm, something elemental analysis will not detect.

The automatic particle counters used at in the laboratory analyse each sample using size channels that range from 4μm to 50μm and will also report the ISO cleanliness code, which makes identifying clean and dirty oils much easier than looking at the raw particle counts.

PQ index

The PQ Index measures the overall ferrous content present within an oil sample.

This content could be comprised of large pieces of metal or tiny particles suspended in the oil. The higher the PQ value, the more contaminated the sample is with ferrous metal.

The PQ Index is a dimensionless value, so the value is not reported using any units. It can detect imminent failures in equipment in some cases where elemental analysis will not.

If gears are chipping in a component, large pieces of ferrous metal may be present in the samples. These larger pieces of metal will be detected by the PQ instrument (if they are ferrous), but not necessarily detected during either elemental or particle count analysis, since these instruments are designed to detect microscopic amounts of metal.

However, the PQ Index will not detect contamination from non-ferrous sources, eg components constructed from aluminium and brass.

Acid/base numbers

The Total Acid Number (TAN) refers to the number of acidic compounds present in the oil. These compounds increase the probability of corrosion occurring within a compartment.

The Total Base Number (TBN) measures the alkaline reserve left in the oil. These additives exist to combat the acidic compounds that can form in the oil through processes such as combustion.

TAN and TBN analysis results are typically used to optimise oil change intervals, instead of changing the oil at fixed periods.

Additional testing

Additional testing is available on oil samples and is included with some of the specialised kits provided by the fluid testing laboratory.

These tests include rapid filtergrams, petane and toluene insolubles, glycol in oil, the remaining useful life of antioxidants evaluation routine (RULER), sugar contamination and ASTM colour.

Rapid filtergrams are included in the premium oil sample test kits and involve analysis of the sample under a microscope, which also includes a quantification of the material, wear mechanism and size.

This test will also include a representative image of the sample, as taken under the microscope, typically at 500 times the magnification.

A graph also accompanies the image, plotting the wear mechanism against the size, showing the overall severity of the contamination.

Pentane and toluene insolubles testing is included with certain premium test kits. This test involves dissolving the oil in solvents to determine the residues left by varnishes and lacquers generated by oil deterioration.

This can be a problem in some highly stressed components, leading to reduced heat transfer and blocking of fine control passages.

Glycol in oil testing is used to detect coolant entry in some types of automatic transmissions.

The RULER test uses anode stripping voltammetry to detect the different species of antioxidants present in the sample. It determines if the antioxidant reserve is still sufficient for continued service or if the oil needs changing. It is a complementary test to TAN/TBN and oxidation by Fourier transform infrared (FTIR) spectroscopy. To have this test performed, producers must purchase the appropriate sample kit and supply new oil in the special sample plug located under the lid.

Source: Hastings Deering

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