Compressor oils

There are many factors which influence the lifespan of an air compressor oil. As a minimum, mineral-based compressor oils should be changed every 2,000 working hours while synthetic-based compressor oils can last up to 8,000 working hours. If there is doubt as to the suitability of an air compressor oil, a sample of the oil may be submitted for analysis and a decision taken based on the outcome of the analysis.

It is best to use an oil that complies with the air compressor manufacturer’s specifications.

In most compressors the oil comes into contact with the gas that is being compressed. The specialised gases used in refrigeration systems can have a chemical reaction with the oil, which will degrade the performance of the oil. Special lubricants have been developed, which are compatible with the gases used in refrigeration systems.

The term “SAE 30” only defines the viscosity of an engine oil. The use of engine oils in air compressors comes from days gone by when lubricants generally weren’t as specialised as they are today. A specialised air compressor oil differs from an engine oil in that it contains reduced levels of detergent additives and elemental sulphur and thus is likely to have a longer lifespan. If a compressor manufacturer recommends oil complying with a particular specification then that is what should be used.

The water in the air compressor receiver comes from the moisture in the air that was drawn in through the compressor’s air intake system. The moisture condenses into water, which accumulates in the receiver. This water can cause the receiver to rust from the inside, eventually weakening it to the point where it can’t hold the air pressure anymore. Draining the air receiver is particularly important in the case of a truck’s air-brake system.