Oil Analysis

A drop of oil heated to 250°C (similar to operating conditions) is deposited on a special absorbent paper, and then placed in an oven. The shape, colour and spread of the stain on the paper provides information on:

• Residual dispersivity of the lubricant
• Fouling of the engine,
• The oxidation state of the oil
• And the possible presence of water particles or fuel oil

This test provides relevant information on the oil’s residual capacity to disperse deposits and allows an assessment of the concentration of carbon in the oil.

Viscosity is the opposite of fluidity: it is the resistance of a liquid to its own flow. It is interpreted relative to that of fresh oil. A good lubricant should have multi-grade viscosity, meaning that it must remain pumpable when cold (so fairly fluid) and yet, withstand very high temperatures without cracking.

The grade of oil is always clearly mentioned on its container (e.g.: 5W40, 5 being the viscosity index when cold and 40 when hot). The viscosity index will vary with use and this test checks the level of variation.
The test is performed at a temperature of 100°C and consists of measuring the time taken for the lubricant to flow into a graduated tube compared to the time a fresh oil of the same grade takes.
This test reveals two observable facts:

• An increase in viscosity means excessive operating temperatures or a high presence of carbon particles resulting from poor combustion;
• A decrease in viscosity implies lubricant shearing or strong presence of unburned fuel.

Every element of matter subjected to very high temperatures excites electrons which become charged with calorific energy. In accordance with the laws of physics, they resume their natural orbit and thus release the energy, but this time in the form of luminous energy. The device (spectrometer) measures the amount of light particles emitted by the oil ingredients to reveal the presence of metal oxides indicating engine wear (normal or abnormal). These are particles of about 2 microns in size.

Phosphorus, zinc, calcium and magnesium are additives that provide the oil with some of its properties. Nickel, aluminium, iron, chromium, molybdenum, copper, lead and tin are produced by wear of engine units. A large presence of silica comes most often from a lack of air filtering. The presence of sodium, boron and potassium indicates the leakage of a coolant fluid.

The purpose of infrared spectrometry is the identification of different molecular bonds in a sample. The infrared spectrum is somehow its “fingerprints”.

Theoretical Approach
The interpretation of a spectrum will tell us about:

• The quality of the oil tested
• Any alteration or degradation in the quality of the oil
• Its possible contamination by foreign bodies

Application to used oil analyses
The main parameters which can be measured by infrared are:

• Carbon number in %
• Water content in %
• Glycol content in %
• Fuel content in %
• Oxidation number (reaction with oxygen)
• Nitration number (reaction with nitrogen)
• Sulphation number (reaction with sulphur)

The principle of this analysis is to measure the deflection of a known, stable magnetic field caused by the presence of ferrous particles and by-products contained in an oil sample.

The result obtained is actually a factor qualifying the presence or absence of large magnetisable particles (mainly iron and occasionally nickel).

This analysis is perfectly complementary to emission spectroscopy because the research is done on small particles.

For more information, please email your queries to:info@sahelienergy.com