AC Compressor Oil Type: Mineral, PAO, POE, PAG Oil, & Purposes – R12 & R134a Refrigerant Oil

Compressor Oil

Your car AC needs enough amount of oil to lubricate the entire system properly. The oil of the compressor is the most crucial and important element for the operation of the cooling system. It is essential to know the different types of oils used in compressor 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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Refrigerant Oil For Car AC


Car cooling system compressor oil is used to lubricate the compressor and the whole cooling system parts. fluids are the fundamental element of car A/C. It provides long service life to the cooling system. It cleans the compressor and other cooling system parts of debris and prevents compressor failure.

As you know that all moving auto parts in the car need lubrication for smooth work. Without enough amount of lubrication, the moving part will eat away due to friction. Similarly, the cooling 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 air conditioning compressor uses different types of oil to lubricate enough the A/C hoses, “O” ring seals, and joints to retain some flexibility.

Related Post: How Car Air Conditioner Works (Animation)

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

AC Compressor Oil Type

The type of fluid required for the cooling system in a car depends on the type of refrigerant used. In a cooling system, every fluid does not fit with every lubricant. Therefore, car compressor manufacturers use the specific refrigerant and type of oil which works best. 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 the cooling systems, and that is “Lubricant Miscibility’. They look for the proper type of oil miscibility with fluid. One type of lubricant will work best with one type of fluid but not with other types because the wrong oil will have different viscosities and other parameters. fluids 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 was one of the important compressor oils over the past years up until 1990. It works best with (R12). It was universal oil at that time. In 1994 the r-134a has dominated the u.s market, which does not work properly with these oils, so a new PAG (Poly-Alkylene-Glycol) Oil was introduced to smoothly work with this fluid. This is a low viscosity oil and a high degree of solvency.

Also, it has good chemical stability and high-temperature tolerance. Mineral oil and PAG oil were used during that time. These are compatible with Alkyl-benzene oil (AB), which can replace in a system where these oils cannot function properly. One example of this is Naphthenic oil.

B. Synthetic Oil

These are oils that are made in laboratories due to chemical reactions. Four types of synthetic fluids are commonly used in automotive cooling systems.

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

Types of Oils that are Synthetic

Manufactured oil has four types, which are explained below.

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

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

Poly-Alkylene-Glycol also called PAG oil was the first Manufactured oil. It has been used in cars since 1995. This is specifically designed and works best with R-134a. There are three different viscosities of PAG oil being used with R-124a called PAG 46 (which is the most popular viscosity oil), PAG 100, and PAG 150. It has excellent miscibility with this new refrigerant. This oil is hygroscopic; 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. You may be wondering at this point if this oil has the property of conduction. It can conduct electricity and can cause a short circuit. So, be careful not to use this oil with a hybrid electrically-driven compressor.

2. Alkyl-Benzene Oil (AB)

Alkyl-Benzene Oil or AB oil is a Manufactured oil for CFC (R-12). It was used in cars built before 1994. One of its properties is that it can mix with the r-12 refrigerant. However, it can not be mixed with R-134a .

And here is another good characteristic of Alkyl-Benzene Oil (AB) is that it does not absorb moisture. Therefore, it was used as a substitute for certain PAG oils by most car manufacturers in the initial era of Air Conditioning.

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

These are manufactured oil, which has been used for many years. It was primarily utilized for retrofitting automobiles that were converted from an R-12 to an R-134a system. Using the wrong oil such as mineral oil in the system would not be compatible with PAG (Poly-Alkylene-Glycol) Oil. As a result, POE oil was used as a substitute for PAG (Poly-Alkylene-Glycol) Oil.

One property of this is that it has an excellent insulating property, Which prevents the electric short circuit of the electrically-Driven-compressor. Such kind of compressor oil was needed to bridge the gap for electric vehicles. It is a widely used compressor oil on the market for the hybrid electric compressor.

4) PAO Oil (Polyalphaolefin Oil)

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

PAO oils are typically used in passenger cars and also in many industrial applications. Using the wrong type of lubrication can 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 Refrigerant 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

POE VS PAG Oil In Car Air Conditioning System

These (Polyol Ester) oil and PAG (Polyalkylene Glycol) oil are both types of lubricating oils used in cooling system and refrigeration systems. The main difference between them is the type of molecule they are made of and their properties.

In car cooling systems, oil like PAG is commonly used due to its favorable properties. This has excellent thermal stability and low volatility, making it well suited for use in high-temperature automotive environments. It also has good compatibility with synthetic refrigerants, which are increasingly being used in car cooling systems.

These oils can also be used in car cooling systems, but they may not be as suitable as PAG (Poly-Alkylene-Glycol) oil due to their tendency to form harmful acids when exposed to high temperatures and humidity. It also has limited solubility with mineral refrigerants and may cause oil separation in systems using R-22 refrigerant.

The Importance of Using Correct PAG Oil in Automotive Air Conditioning Systems

Evacuating The Air Conditioning System

Stringent vehicle engineering standards have led to advancements in automotive cooling system technology especially in compressor oils over the past two decades. Mineral oil was the de facto lubricant used in these systems, but due to its ozone depletion properties, it has been phased out and replaced with a special type of oil like poly-Alkylene glycol (PAG) oil.

This is mixed well with the new refrigerants, such as R134a and R1234yf, that have been introduced to replace older, more harmful refrigerants. However, it is important to use the correct PAG oil with the appropriate thickness values and amount for each specific system to ensure optimal performance and prevent potential damage. Using the wrong type or amount of this oil can result in reduced efficiency, increased wear, and tear, and contribute to global warming potential.

Frequently Asked Questions (FAQs)

What are compressor oils that techs need, and why are they important for vehicle cooling systems?

Compressor oils are special formulations that lubricate and protect the internal components of cooling system compressors. Techs need to use the right type and thickness value of compressor oil to ensure the proper operation and longevity of the compressor.

How has the discontinuation of r-12 necessitated the use of r-1234yf in cars?

R-12 was a widely used refrigerant in cars, but due to its ozone-depleting properties, it has been phased out and replaced with R-134a. While R-134a does not deplete the ozone layer like R-12, research has shown that R-1234yf possesses strong cooling properties and low GWP. For this reason, newer more environmentally friendly refrigerant like r-1234yf was developed. The introduction of r-1234yf has put the onus on shop owners and technicians to be stocked with the proper refrigerant and equipment.

Can thinner oil formulations for cars lead to a number of issues?

Thinner oil formulations for the cars can provide some benefits, such as improved fuel efficiency and engine performance. However, they can also lead to a number of issues, such as increased engine wear and reduced oil pressure, especially in older or high-mileage vehicles.

What is a popular thick oil for cars, and how does it affect engine performance?

A popular thick motor oil for cars is 5W-30, which is commonly recommended by vehicle manufacturers. This oil provides a good balance of protection and performance in most driving conditions, but it’s important to use the oil viscosity that’s specified for your vehicle to ensure optimal performance.

What can happen if a certain compressor used in a vehicle rolls into a shop with a low oil level?

If a vehicle with a cooling system compressor rolls into a shop with a low oil level, it can lead to serious damage to the compressor and other parts of the system. Techs should always check the oil level and use the proper compressor oil formulations to avoid costly repairs and ensure customer satisfaction.

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