5 Misunderstandings About Industrial Oil Lubricants Used in Air Compressors


The industrial oil lubricants used in air compressors are often misunderstood and underestimated. This idea sometimes leads to serious consequences, including but not limited to choosing the wrong air compressor, unreasonably decrease of air compressor efficiency, frequent air compressor failures, etc.

These situations will make your air compressor difficult to use and annoying. You may wonder why my air compressor is of such poor quality, but in fact, it may be simply because you did not use the lubricants correctly. Let Kotech show you why industrial oil lubricants are so critical and how to make good use of it through this page.

What is the industrial oil lubricant in air compressor?

5 Misunderstandings About Industrial Oil Lubricants Used in Air Compressors

Applications of industrial oil lubricants in air compressors

It should be noted that, except for several emerging oil-free air compressors that do not use oil for lubrication and air compressors that do not use any lubricants, almost all air compressors use industrial oil lubricants.

The definition of oil-injected and oil-free air compressors is based on whether the final product—compressed air contains oil, not whether the air compressor uses industrial oil lubricants. Oil-injected air compressors rely on the special oil (mineral oil or compound oil) of the air compressor to mix, compress, and separate the air before entering the purification equipment.

Oil-free means that there is no lubricant in the compression chamber of the air compressor, but the accessories outside the compression chamber will still use oil lubricants. It may also be possible to replace the oil with another lubricant, such as water lubrication, or directly run without any lubricating medium.

Therefore, lubricants are essential for the continued reliability, efficiency and overall service life of the compressor and its various wear parts in most air compressors.

It is worth noting that some air compressors are marked as “technically oil-free” but in fact their final product – compressed air still contains a small amount of oil, because the standard they implement is the ISO (International Organization for Standardization) Class 1, which stipulates that compressed air with an oil concentration of 0.01 mg/m³ at 1 bara (14.5psia) and 20°C (68F) is “technically oil-free”.

Now there is a new standard ISO Class 0, which stipulates that only 100% oil-free compressed air can be certified. So when choosing an oil-free air compressor, please make sure you choose a truly oil-free air compressor, not a “technically oil-free” air compressor. For more details, please check our previous article:(Two different types of compressors oil less vs oil flooded which is better)

What is the industrial oil lubricant in air compressor

Functions of industrial oil lubricants in air compressors


When the compression parts are running, high-speed friction will occur. At this time, the sprayed air compressor oil lubricants will form a lubricating film on the surface of the internal parts of the air compressor, which can reduce the friction coefficient and decrease the direct contact between metals, thereby reducing the friction and wear between metal parts, lessen friction heat and energy loss, and maintaining good operating condition of air compressor.


The compression parts of the air compressor will generate considerable heat during high-speed friction. If the heat cannot be dissipated in time, the high temperature of the machine will lead to a failure. Industrial oil lubricants can not only transfer heat to the machine casing, but also absorb a large amount of heat due to its characteristic of high heat capacity. Thus playing a cooling role in air compressor and preventing machine parts from overheating and getting stuck.


Air compressors need an airtight space to fully compress the air during high-speed mechanical operation, industrial oil lubricants can use its surface tension and viscosity characteristics to seal the parts and components to form a closed layer while lubricating friction to prevent air from running to other places during the compression process and causing air leakage, thereby ensuring the normal operation of the air compressor. This is very important for the normal operation of the air compressor, because air leakage will not only lead to a decline in equipment performance, but also affect the user’s production efficiency. Know more about air leaks and solutions.

Cleaning and anti-corrosion

KOE Series screw compressorThe inside of the air compressor must keep clean, otherwise the parts will be contaminated by dust and other impurities in the air, which may cause air leaks, dust accumulation. However, as the machine working, some dirt will naturally form. Industrial oil lubricants can dissolve some dirt in a way similar to a cleaning liquid or solvent, playing a cleaning role.

In addition, industrial oil lubricants is equivalent to adding a protective film to the surface of each component, which has the effect of isolating the air and can also absorb impurities in the air, so that the internal parts will not be oxidized by oxygen in the air, thereby reducing the occurrence of rust on these parts and protecting the internal parts from corrosion by external substances and water vapor.


Composition of industrial oil lubricants

The base oil

The base oil of industrial oil lubricants in air compressor generally accounts for more than 95% of the finished oil. Therefore, the quality of the base oil is directly related to the quality level of the finished oil of industrial oil lubricants, and the quality of the base oil is directly related to its refining depth.

The base oil with a deep refining depth has less heavy aromatics and colloid content; the residual carbon lower, the sensitivity of the antioxidant better, the quality of the base oil higher, it has a small tendency to deposit carbon in the compressor system, good oil-water separation, and a relatively longer service life. The base oil of industrial oil lubricants can be divided into two categories: mineral oil type and synthetic oil type.

Composition of industrial oil lubricants

The production of mineral oil industrial oil lubricants is generally obtained by solvent refining, solvent dewaxing, hydrogenation or clay supplementary refining to obtain the base oil, and then add a variety of additives to blend it.

The base oil of synthetic oil type is an organic liquid base oil obtained by chemical synthesis and then blended or added with a variety of additives to make a lubricant. Most of its base oils are polymers or high molecular organic compounds. There are many types of synthetic oils. The synthetic oils used as industrial oil lubricantss mainly include synthetic hydrocarbons (poly-α-olefins), organic esters (diesters), Snort lubricants, polyalkylene glycols, fluorosilicone oils and phosphate esters.

The price of synthetic oil industrial oil lubricants is much more expensive than that of mineral oil industrial oil lubricants, but the comprehensive economic benefits of synthetic oil exceed those of ordinary mineral oil. It has oxidation stability, low carbon deposition tendency, can be lubricated outside the temperature range applicable to ordinary mineral oil, has a long service life, and can meet the use requirements that ordinary mineral lubricants cannot bear.


Additives are added to improve the performance of base oil and extend its service life. Adding the right additives can change the physical and chemical properties of industrial oil lubricants, strengthen its functions in a certain aspect or give it new functions. Additives are also an important way to obtain high-quality industrial oil lubricants.

Common additives include antioxidants, anti-wear agents, defoamers, anti-emulsifiers, cleaning agents, anti-corrosion agents, etc.

Antioxidants are mainly used to prevent the influence of air oxidation on industrial oil lubricants, which can improve the stability of industrial oil lubricants, resist oxidation, and extend its service life. The addition of anti-wear agents can improve the anti-abrasion performance of industrial oil lubricants and reduce the wear and tear of air compressor parts.

Defoamers can reduce the influence of bubbles in oil on lubrication and improve air separation. Anti-emulsifiers can improve the hydrophilicity and emulsification properties of air compressor oil, making it easier to disperse evenly.

Cleaning agents can enhance the cleaning ability of industrial oil lubricants, so that it can more effectively remove dirt such as carbon deposits. Anti-corrosion agents can improve the corrosion resistance of industrial oil lubricants and reduce the corrosion of air compressor parts.

Are you looking for a reliable and efficient power source for your industry? Kotech dealers are experienced in finding the perfect air compressor for your needs.

Contact your local Kotech dealer today and discover how an air compressor can increase your productivity and safety.

Misunderstandings on using and changing the industrial oil lubricants

The more industrial oil lubricant added, the better

The main function of industrial oil lubricants is to lubricate machinery, reduce friction and wear. Insufficient oil will accelerate the deterioration of lubricants and even cause adhesion and abnormal wear of parts due to lack of oil. However, too much lubricant is not advisable for two reasons: first, too much lubricant will enter the combustion chamber from the gap between the cylinder and the piston to produce carbon deposits; second, it increases the stirring resistance of the crankshaft connecting rod, which increases fuel consumption.

Experiments show that when the amount of refueling exceeds the standard by 1%, fuel consumption will increase by 1.2%. Therefore, refueling must follow the principle of “small amount, frequent refueling” to keep the oil in an reasonable level.

The higher the viscosity of industrial oil lubricants, the better

Many people believe that the higher the viscosity of industrial oil lubricants, the better, and the higher the grade of industrial oil lubricants (centistokes of kinematic viscosity at 100°C), the better.

In fact, this understanding is one-sided. The higher the viscosity, the thicker the oil film between the friction surfaces of the moving parts. Although a thick oil film is beneficial to prevent wear of the friction surface, it also increases friction resistance and power loss. Authoritative data show that if the viscosity of industrial oil lubricants is reduced by 1 centistoke, fuel can be saved by about 1.5%.

In addition, experiments have also proved that when the viscosity of industrial oil lubricants exceeds the requirements, it will also increase the wear of machine parts, because about 2/3 of the wear of machine parts occurs at the beginning of starting.

When using a lubricant with high viscosity and starting at low temperature, the lubricant on the friction surface has been lost after a period of shutdown, and the high viscosity and slow flow cannot be replenished to the friction surface in time to form a lubricant film, so the machine parts will be in a state of dry friction and semi-dry friction for a long time, resulting in increased wear of the machine parts.

Therefore, the viscosity of the air compressor lubricant is not the higher the better, but the lubricant with a low viscosity should be used as much as possible under the condition of ensuring lubrication.

Generally speaking, it is most appropriate to use OEM lubricant or recommended lubricant. If the OEM lubricant is used up and you don’t know which oil to choose, it’s a good choice to seek the support of professional technicians. Kotech got an expert team and is always ready to help you at any time, contact us for free.

Only change the industrial oil lubricants when they are used up

Some people may think that lubricating oil does not need to be replaced as long as it is not used up. If there is not enough oil, just add some new. This practice is unscientific, because the quality of lubricating oil is a key factor affecting the reliability and service life of the air compressor. Timely replacement of lubricating oil is the guarantee of reliable lubrication of the air compressor. During the use of lubricating oil, the quality will gradually decline due to pollution, oxidation and other reasons.

At the same time, there will be some consumption, which will reduce the amount. Continuously adding some new oil can only make up for the lack of quantity, but cannot completely compensate for the loss of lubricating oil performance. As time goes on, the performance of lubricating oil will become worse and worse, which will have a serious impact on the air compressor.

For example, the sediment in the air compressor will increase sharply, the power performance will decrease, the parts will wear out early, and finally lead to functional failures.

In order to ensure the long-term efficient operation of the air compressor and reduce components wear, the lubricating oil must be replaced in time according to the OEM recommended standards and users’ own usage.

It doesn’t matter if different brands of lubricants are mixed

From the perspective of cost saving, during seasonal maintenance, people may be reluctant to replace the remaining lubricating oil in the air compressor, then continue to use it after adding a certain amount of new oil.

Sometimes, they simply mix two different brands of lubricating oil. This approach may seem to be fine for the time being, but in the long run, it accelerates the wear, aging and deterioration of the machine parts, and the cost increases. Lubricating oils (or hydraulic oils) of different brands cannot be mixed.

Because the physical and chemical properties of lubricating oils of different brands are different, their main components and indicators such as chemical composition, viscosity, acid value and various additives (anti-wear agents, preservatives, antioxidants, rust inhibitors) directly affect the operation of the machine parts. If mixed, their performance will change, the operating temperature of the machine parts will increase, a large number of bubbles will be generated, and even deterioration will occur.

The working conditions of the air compressor precision parts, operating parts, and seals will also change, performance will be reduced, mechanical damage will be accelerated, seals will deteriorate and age, and poor sealing will cause air leakage, etc.

If the color of industrial oil lubricant turns, replace it immediately

When the color of the lubricating oil turns dark, people may consider that the oil has seriously deteriorated, and then replace it immediately, which can cause waste of oil. For the lubricating oil that did not add detergent dispersant in the early days, the color turning black during use is indeed a manifestation of serious deterioration of the oil, but the lubricating oil used now generally contains detergent dispersant, the purpose is to wash off the rubber film and black carbon deposits adhering to the piston, and disperse them in the oil to reduce the generation of high-temperature deposits in the air compressor. Therefore, the color of the lubricating oil is easy to turn after a period of use, but the oil has not deteriorated at this time.

Whether the lubricating oil in use is seriously deteriorated and needs to be replaced should be mainly determined based on whether the physical and chemical indicators of the lubricating oil meet the scrap standard.

The change period of industrial oil lubricants should be appropriate. Too early will cause lubricating oil waste, and too late will increase the wear of the air compressor and shorten the maintenance cycle and service life of the air compressor. Generally, the oil should be changed according to the period specified in the instruction manual. According to practical experience, the following methods can be used for reference:

Lubricating oil viscosity change experiment

Use two glass tubes with a diameter of about 1 cm and a length of about 30 cm, one filled with new oil and the other filled with the lubricant currently in use. Fill until there is a gap of about 0.5 cm, seal tightly, and at the same temperature, turn them upside down and press the stopwatch at the same time to record the number of seconds required for the bubbles in the two tubes to rise to the top. If the difference between the two exceeds 1/4, the oil should be changed.

Oil stain test method

Drop a drop of new lubricant and a drop of lubricant currently in use on two clean filter papers, respectively, and observe. If the boundary between the black spot in the middle of the lubricant in use and the surrounding yellow oil stain is not very obvious, and it is gradually spreading, it means that the clean dispersant in the lubricant has not been exhausted and it can continue to be used. If the boundary between the black spot in the middle and the surrounding yellow oil stain is clear and there is a clear dividing line, it means that the clean dispersant in it has failed and the oil must be changed.

Sedimentation test method

Take 100g of the lubricating oil in use, add about 200g of colorless gasoline to dilute it, filter it with ordinary filter paper, then dry the filter paper and the sediment on the paper, and weigh it. If the mass exceeds 59g, the oil should be changed.

kotech group oil free air compressor and industrial oil lubricants


Air compressor oil is mainly used for lubrication of compressor cylinder moving parts and exhaust valves, and plays a role in rust prevention, corrosion prevention, sealing and cooling. Since the air compressor has been in an environment of high pressure, high temperature and condensed water, high-quality air compressor oil should have excellent high-temperature oxidation stability, low carbon deposition tendency, suitable viscosity and viscosity-temperature performance, good oil-water separation, rust prevention and corrosion prevention, etc.

The oil change standard of the air compressor mainly depends on factors such as the type and quality of the oil, the working environment and operating time.

Generally speaking, the frequency of lubricant replacement can be determined by combining the operating manual from OEM, the working environment and working intensity of the air compressor, and the operating time of the air compressor. If the air quality in the environment is poor or there are corrosive substances, the oil may need to be replaced in advance.

In addition, the newly purchased air compressor must be replaced with new oil after 500 hours of operation, and then it can be changed according to the normal oil change cycle. If you don’t know when your air compressor needs to change the lubricant, or don’t know which lubricant to choose, you can seek help from professional technicians.

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