Oil Analysis

Chemical Makeup: FTIR

• Fourier Transform Infrared Spectroscopy
• Common method to assess the oxidation level (or potential) in oil
• Especially useful because it allows the analysis of the additives and the presence of a variety of contaminants.
• Some of the molecules that can be tested with this method include water, oxidation by-products, nitration, sulphation, glycol, anti-oxidants, anti-wear, soot and many more.

• Method:
• Infrared light passed through a fixed film of oil (~100 um thick)
• Absorbance of IR is examined at range of wavelengths
• Compared to the same test on "base", or new oil. 
• Many of the molecules being tested for (additive, contaminant molecules plus the oil molecules) absorb the IR light only at very specific wavelengths. By comparing the used oil to the new oil, an accurate assessment of the quantity and presence of these molecules can be made.

Transmittance Spectra – Engine Oil

• NEW

• USED

Chemical Contaminants

• Some generated by processes taking place in the oil (e.g. oxidation)
• Others are result of outside chemical contaminants getting into the oil and include:
• Water
• Glycol
• Fuel
• Air

Chemical Contaminants: Water

• Water is possibly the single most destructive contaminant that commonly gets into oil. It can get into the oil in any number of ways:
• Oil drum stored improperly, water standing on top slowly leaks in.
• Reservoir that gets water condensation on the lid, eventually drips back into the oil.
• Leaking or no seals
• Often people make the mistake of thinking that since oil and water separate (oil on top, water on the bottom), you can see water contamination.

Effects of Water Contamination

• Causes oxidation -significantly worse when water is present. The chemical process causes acid formation, sludge and varnish are formed and the oil is thickened.
• Viscosity changes - Contrary to what many suspect, water will cause the viscosity to increase (oil thickens) especially when oil emulsions are created.
• Dielectric changes - Water, since it conducts electricity, reduces the insulating properties of oil.
• Aeration - Water can accelerate aeration problems such as the formation of tiny air bubbles and the generation of foam.
• Attacks additives - Water chemically reacts with additives to cause effects such as sludge, acids, sediment and many more.
• Reduces oil film strength - Water will cause film failure and other side effects.
• Bacteria - Bacteria can actually can form in the water.
• Water also affects machine components:
• Corrosion - Water causes components to rust (one of the solid contaminants mentioned previously).
• Acids - The acids formed will also cause corrosion. Embrittlement - Loss of oil film strength and instantaneous water vaporization can cause hydrogen embrittlement of the metallic components.