Types Of Compressor Oil: Mineral, PAO, POE, PAG Oil, & Purposes

Compressor Oil

Your car AC needs enough amount of oil to properly lubricate the entire system. Compressor oil is the most crucial and important element for the operation of the Air Conditioner. It is important to know the different types of compressor oils and their purposes.

In this powerful article, you are going to learn the car compressor oils, especially Mineral, PAO, POE, AB, and PAG oil, and their purposes.

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AC Compressor Oil For Car


Car air conditioner compressor oil is the lubrication oil used to lubricate the compressor and the whole air conditioning system parts. Lubricants are the fundamental element of car A/C. It provides long service life to the air conditioning system. It cleans the compressor and other air conditioner system parts of debris.

As you know that every moving part in the car needs lubrication for smooth work. Without enough amount of lubrication, the moving part will eat away due to friction. Similarly, the Air Conditioning system parts are subjected to continuous vibration. So, it is necessary for the A/C parts to be flexible enough to stand with vibration.

Therefore, the compressor oil is used to lubricate enough the A/C hoses, “O” ring seals, and joints to retain some flexibility.

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This is an Info
Too much oil in car air conditioning can reduce the system’s cooling, and too little can lead to compressor friction.

Types Of Compressor Oil

In-car air conditioners and different types of refrigerants need different kinds of lubricants. In air conditioning, every refrigerant does not fit with every lubricant. Therefore, car manufacturers use the specific refrigerant best works with the specific lubricant. The reason you might don’t know, but keep reading I am about to explore it.

The point is that car manufacturers look for one significant factor in the smooth working of air conditioning, and that is “Lubricant Miscibility’. They look for lubricant miscibility with refrigerant. One type of lubricant will work best with R-12 refrigerant but not with R-134a. Lubricants and refrigerants must be compatible with each other for the best A/C performance.

Remember, there are two categories of oils commonly used in automotive air conditioning.

  1. Mineral Oil
  2. Synthetic Oil

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A. Air Conditioner Mineral Oil

Mineral Oil
Mineral Oil

Mineral oil is the first oil used in automobiles up until 1990. It works best with R-12 refrigerant. In 1994 the r134a refrigerant was developed, which does not work properly with mineral oil, so a new PAG oil was introduced to smoothly work with the r134a refrigerant. Mineral oil has low viscosity and a high degree of solvency. Also, it has good chemical stability and high-temperature tolerance.

Mineral oil is compatible with Alkyl-benzene oil (AB), which can replace in a system where mineral oil cannot function properly. One example of mineral oil is Naphthenic oil.

B. Synthetic Oil

Synthetic oils are oils that are made in laboratories due to chemical reactions. Four types of synthetic lubricants are commonly used in automotive air conditioning.

This is an Info
The bigger compressor needs high-viscosity oil because of the high gaps in system parts. And the system needs high viscosity thicker oil for optimum working.

Synthetic Oil Types

Synthetic oil has four types, which are explained below.

  1. PAG Oil (Poly-Alkylene-Glycol Oil)
  2. Alkyl-Benzene Oil (AB)
  3. POE Oil (Polyol-Ester Oil or Ester Oil)
  4. PAO Oil (Polyalphaolefin Oil)

1) PAG Oil (Poly-Alkylene-Glycol Oil)

Poly-Alkylene-Glycol also called PAG oil was the first synthetic oil. It is used in cars since 1995. PAG oil is specifically designed and works best with R-134a refrigerant. It has excellent miscibility with R-134a. It is hygroscopic oil; which means it absorbs the water molecules and makes the oil acidic in nature, which drives corrosion.

Moreover, it is chemically stable with A/C even, at high-temperature. PAG oil has three different types of viscosity called PAG 46, PAG 100, and PAG 150. You may be wondering at this point if PAG oil has the property of conduction. It can conduct electricity and can cause a short circuit. So, be careful not to use it with a hybrid-electrically-driven compressor.

2. Alkyl-Benzene Oil (AB)

Alkyl-Benzene Oil or AB oil is a synthetic oil used with CFC (R-12) refrigerant. It was used in cars built before 1994. One of its properties is that it has excellent miscibility with R-12 refrigerant. But, conversely, it does not mix with R-134a refrigerant.

And here is another good characteristic of Alkyl-Benzene Oil (AB) is that it does not absorb moisture. Which attracted most of the car manufacturers in the initial era of A/C.

3. POE Oil (Polyol-Ester Oil Or Ester Oil)

POE Oil also called Polyol-Ester Oil or Ester Oil is synthetic oil, which has been used for many years. It was mainly used for retrofit cars which are used to convert from R-12 to R-134a system. As mineral oil in the system would not work with PAG Oil so, polyol ester oil is used instead of PAG Oil. It comes only in one viscosity.

One property of ester oil is that it has an excellent insulating property, Which prevents the electric short circuit of the electrically-Driven-compressor. It is widely used in the hybrid electric compressor.

4) PAO Oil (Polyalphaolefin Oil)

Polyalphaolefin Oil also called PAO Oil is a synthetic oil having very low hygroscopic properties. It does not absorb as many water molecules as PAG oil does. It is compatible with many lubricants and refrigerants.

PAO oils are used in passenger cars and also in many industrial applications. If the wrong lubricants are used with refrigerants, they may react. If in case a chemical reaction occurs, sludge and acid may be formed, which can badly affect the performance of the compressor. Therefore, use the right amount of oil in the right quantity. Always check manufacturer recommendations in the service manual.

Related Post: 3 Types Of Car AC Refrigerant, Freon R-12, R-134a, R-1234yf

Purpose Of The Compressor Oil

Mainly lubricants have three main purposes, which are mentioned below.

  1. To lubricate the moving parts to reduce friction
  2. To remove frictional heat
  3. To seal the hoses and “O” rings

Frequently Asked Questions (FAQs)

Which oil is used in the AC compressor?

The type of oil used in an AC compressor can vary depending on the manufacturer. However, most compressors use either synthetic or mineral oil, as they provide superior lubrication and cooling properties. Synthetic oils are also more resistant to breakdown under high temperatures and pressures, making them ideal for use in compressors.

What type of oil do you use with R134a?

The refrigerant R134a is a hydrofluorocarbon (HFC) that has been widely used as a replacement for the ozone-depleting refrigerant R12. Unlike R12, however, R134a is not compatible with mineral oils such as petroleum oil or mineral oil. Instead, it must be used with synthetic oil such as polyalkylene glycol (PAG).re likely it is that synthetic oil will be used. This oil is used because it has a low viscosity and is compatible with the R134a refrigerant. The PAG oil is also used because it does not cause any damage to the seals or hoses in the refrigeration system.

Is engine oil OK for the compressor?

No, engine oil is not OK for a compressor. While it may seem like a good idea to use engine oil as a lubricant for your compressor, it will actually damage the unit. Engine oil is designed for engines, not compressors. It has the wrong chemical makeup to be used as a lubricant in a compressor and will break down the seals and gaskets, leading to leaks.

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