Oils and Lubricants for Air Compressors

Are you using the right oil – compressor oil, that is? Lubricants, especially oils for compressors that are designed for industrial use, are specifically developed and tested for the respective compressor type and requirements. The main tasks of a compressor oil include reducing typical wear and tear, cooling, sealing, and cleaning. There are also a few more fun, relevant facts about compressor oils that you should be aware of when planning for maintenance of your compressed air system.

What Does Air Compressor Oil Actually Do?

Compressor oil is a critical component of maintaining a healthy compressed air installation. Primarily a coolant, oil removes the heat generated during the compression process. A quality compressor oil reduces the wear and tear on rotating parts by using various additives to prevent metal from rubbing against metal; in other words, the oil cools the system so that the element doesn't overheat.

Oil also lubricates the rotors and seals the compression chamber. Because compressor oil is used for cooling and sealing, it must be special, high-quality oil and cannot be substituted with alternatives such as motor oil. Essentially, as the oil flows around between the screw elements, it seals the space in which the air is compressed. Another important task is cleaning. In some situations, dust enters the machine through the air filter. The oil picks up these particles, carries them to the oil filter, and flows back. Keep in mind that if your compressor oil fails, or doesn’t lubricate as it should, the internal compressor components can be quickly destroyed.

Types of Air Compressor Oil

There are two main types of compressor oil: standard oil (also called mineral oil) and synthetic oil.

1. Standard (Mineral) Compressor Oil. Standard compressor oil is made by using a mineral base and are cheaper than synthetic compressor oil. Mineral oil is more volatile and is more likely to evaporate than synthetic oil. As a result, it is used up faster. It also has a higher oil carry-over, so it can get into the compressed air network despite the downstream components such as the oil filter and oil separator. Mineral oils are also significantly more reactive than synthetic oils. The carbon chains are not 100% saturated with hydrogen, which means that the oil reacts faster with other substances and can form clumps. This shortens the service life of the oil and the service life of the filters and oil separators. This type of oil is typically recommended for use in compressors that aren’t used continuously, or for homeowners/DIY’ers whose applications are lighter in nature.
   
   
2. Synthetic Compressor Oil. Synthetic compressor oil is made with – you guessed it! – a synthetic base. This type of oil is a higher-quality, premium product that has a longer service life; in fact, synthetic oils can run typically run 50% longer than standard oils. Synthetic oils can also extend the life of your compressor, are consumed at a slower rate (which equates to adding oil less often), stay cooler than their standard oil counterparts, and also can help in reducing various deposits that negatively impact compressor performance. Another benefit? Synthetic oil doesn’t contain sulfur or additives, which helps with preventing buildup on valves.

Be Careful with Universal Compressor Oils

Some compressed air manufacturers will recommend one oil for multi-purpose applications (piston compressors, screw compressors, etc.). However, different machines have different requirements, which means that one universal and alternative oil cannot achieve the highest performance of the specific compressor. The result is a significantly lower efficiency and protective property.

What Determines a Compressor Oil’s Life Span?

Heat, not oil reservoir size, determines how long oil lasts. If a compressor is experiencing shortened oil life or requires a larger oil reservoir, the compressor may be generating more heat during compression. Another possible problem is that excess oil is passing through the rotors because of an unusually wide gap. Ideally, operators should consider the total cost of changing oil per running hour and be wary of compressors with oil life expectancy far shorter than the industry average. To find out the average oil life expectancy and oil capacity of an oil-injected screw compressor, refer to compressor’s operator’s manual.

Questions on what type of compressor oil is best suited for your compressor installation?