Can I Use Motor Oil in My Air Compressor? – Mechanic’s Opinion

Last week, I was poking around forums and a topic got noticed, “Can I use motor oil in my air compressor?”

Although it was not the question, what surprised me most are the answers from those fellows who are all using different compressors from different manufacturers and expressing their opinion based on their experience.

Can You Use Motor Oil in Your Air Compressor

If you are in a hurry I have a straightforward answer – you can use motor oil in your compressor only if it is engineered to use motor oil and you just need to look at the user manual to be sure, if you have lost it, use a 20W ISO 68 or 30W ISO 100 non-detergent one. Don’t ever use regular motor oil for Compressor if you don’t want to kill it.

Kill the compressor! – You may ask.

And my answer is using the wrong oil in your compressor will not kill it immediately buy in real sooner than you expect. And performance? – You can’t expect a good yield if you don’t feed it well.

So if you are curious about why you shouldn’t use an alien oil in your air compressor and want to know the real scene behind it; then I’m helpless to say that we have to start from very basic and you have to hold on for a little longer.

What Happens When You Use Motor Oil in Air Compressor

Later, I talked about the difference between air compressor oil and motor oil, you will know that the properties of these two oils vary on a number of things. Therefore, using motor oil as an air compressor oil substitute will lead to unexpected behavior from the compressor and that is due to –

  • Detergents present in motor oil will foam up when gets agitated and the oil with foam won’t lubricate well.
  • Additives of Motor oil will cause carbon build-up at high temperatures.
  • It will leave a deposit in the pump and hence will decrease its power and capacity.
  • The best performing temperature and other conditions of these two oils aren’t the same for example their viscosity, pour point, etc. This will lead to the dysfunction of oil. Again there is a remarkable difference in the working temperature of a motor engine and an air compressor.
  • Some of the additives of motor oil are totally useless for the compressor and hence can damage the quality of the air.
  • Finally, despite having air filters, it’s for sure, that the use of a motor or an alien oil in the compressor will hart the quality and purity of compressed air.

What Kind of Oil to Use in Air Compressor

  • Always try to use the recommended air compressor oil as the compressor is engineered to use that oil.
  • Prefer the inorganic and non-detergent ones.
  • If you don’t know which one to use and it’s hard to get the exact one, use 20W ISO 68 or 30W ISO 100 oil. They are the most commonly used ones.
  • A 30W single viscosity non-detergent inorganic oil will be fine with most of the compressor.
  • If you can, make sure you have one with Monolec that works best as a wear-reducing agent creating a single molecular film over the metal surface.

For a better understanding of the consequences of using motor oil in an air compressor, the following basics will help you.

Functions of Oil in Air Compressor

In an air compressor, oil-primarily performs 4 different types of tasks.

  • Cooling: as the air compressor compresses air continuously, the temperature inside the compression chamber gets higher. This can lead to failure of the compressor and oil is used as a coolant.
  • Lubrication: A number of moving parts are the key to getting compressed air and as all of them are made of metal, proper lubrication is important to so that they can perform their task. Lubrication is the major task of an air compressor and it gives protection from wear and corrosion.
  • Sealing: Sealing is most important to compress the air and keep it in a compressed state. But sometimes, this is not achievable only by sealing with metal parts. Oil can reach the smallest thinkable position and can give a good sealing
  • Cleaning: Although the air filter can capture most of the contaminant particles, some nanoparticles are still present in the air. Oil is a good medium to capture them. Again the metal parts of the compressor produce fragmented small particles in its service time. These particles need to be removed from the compression chamber for maximum efficiency and service life. Oil is also good at this job.

What is an Engine or Motor Oil & Its Properties?

Engine or motor oil can be synthetic or organic contains different additives and is used for lubrication in the continuously moving metal parts of an engine.

Now you may ask if the oil itself is a good lubricator then why use additives? You know how hot it is inside of an engine and oil without additives will deteriorate soon at such temperature. Who wants to count money for engine oil every month?

What is an Air Compressor Oil & its Properties?

Air compressor oil – a special type of oil that is usually synthetic that doesn’t contain detergent (note that motor oil contains detergent) and is used for lubricating the ball bearings or screws (in Screw Air Compressor) and other parts. Another key function of compressor oil is to keep the compressor valves free from carbon buildup and increase its service life and efficiency.

Air Compressor Oil vs Motor Oil

There can be a lot of talk on the differences between motor oil and Compressor Oil – from origin to pour point or ingredients to viscosity index. But the key difference is the presence of Detergent (i.e. calcium sulphonate, barium, and magnesium sulfonates and alkylphenols) in Engine oil and its absence in Compressor oil.

What Does Detergent Do Actually?

In 1930 detergent was first introduced in engine oils. You may think that they are something you use for cleaning at home; but not. It has two basic functions, neutralizing the acids and keeping the hot metal components of an engine free from deposits.

The second one is the most important property for its usability in the motor engine and will also help us to understand why an air compressor oil doesn’t contain it.

How detergent additives perform is really easy to understand, they just catch up the particles from the metal parts of an engine and let them settle down. Later, they are deposited in the bottom and taken out with the old oil when you change the oil.

Why We Don’t Mix Detergent With Air Compressor Oil?

To understand the reason for not using detergent in air compressor oil let’s have a look at what happens when you don’t use detergent in oil.

When we don’t have those detergent agents present in the oil, the oil will still catch those fragmented particles from the metal parts of the compressor. But, because of the absence of these detergent agents, they will not be settled down or deposited in the bottom. Just like coagulation, the oil will carry those particles and when it will go through the oil filter, the filter will capture them.

Therefore, the use of detergent in the air compressor will leave deposits in the pump and also cause carbon build-up in the valve.

The result? Lower efficiency and shorten service life.

Every machine is unique and they are engineered to use specific types of things to run properly. Changing them will hart the efficiency or life expectancy of the machine for sure. The same is applicable to an air compressor.

Therefore, always try to use manufacturer-recommended oil and don’t use motor oil in your compressor if you expect a good service from your compressor.

2 thoughts on “Can I Use Motor Oil in My Air Compressor? – Mechanic’s Opinion”

  1. wish my people understand all this, I cant find the non-detergent oil in the whole country,,, they all use regular motor oil.


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