Used oil analysis is a systematic approach to monitoring equipment performance. A lubricant sample is taken, sent to the laboratory for analysis, and the results are then sent back to the person who sent in the sample. The results typically include physical property tests and wear metal analyses.

What can oil analysis do for you?

• Establish safe and proper drain intervals.
• Provide a reduction in unforeseen breakdowns.
• Reduce down time.
• Provide a reduction in the number of oil changes and labor costs.
• Provide overall maintenance savings.
• Provide longer equipment life.
• Eliminate unnecessary overhauls.
• Provide better fuel mileage.
• Provide support for equipment warranty claims.

There are three ways to obtain a representative sample of used oil from an engine: Drain plug method, sample gun method, and petcock method. It is probably most convenient to use the “drain plug method”. Be certain to take the sample after the engine has been operated at normal operating temperature for several hours. Drain the oil while the engine is warm. Loosen the drain plug and let a small amount of oil drain into the drain pan before catching the sample to be sent to the laboratory. This ensures that any contamination surrounding the drain plug will not be present in the sample and influence the test results. Never take samples from the drain pan.

Wear metal tests are used to interpret the condition of the equipment components. There are certain combinations of elements that indicate certain problems. Tin, lead, and copper may all indicate bearing wear. Iron combined with chromium will usually indicate liner and ring wear, possibly along with aluminum, which would also indicate piston wear. Silicon can usually be traced to a faulty air intake system which is allowing raw air into the combustion chamber. This air carries with it dirt or sand which can destroy the inside of an engine. Boron and sodium are components of ethylene glycol and usually will indicate antifreeze is present in the oil. This is usually the result of a blown head gasket, leaky oil cooler, or cracked block.

Physical properties tests are performed on a FT-IR spectrophotometer. The used oil is compared to fresh unused oil. Soot level is an indicator of combustion efficiency. Oxidation is a measure of the effective service life of the oil. Nitration measures nitrogen compounds in the oil resulting from blow-by past the compression rings. High levels of ZDDP depletion indicate that the additive is being used up. Water and fuel dilution are also measured. Viscosity measures a lubricant’s resistance to flow. Changes in viscosity indicate improper servicing, dilution or contamination and lubricant breakdown in service.