Level 1, Unit 2, Section 1 – 1.4 Refrigerant Oils & Lubricants

Unit 2 — Introduction to Refrigerants & Handling Practices

Section 1 — Refrigerants, Gases and Oils

1.4 Refrigerant Oils & Lubricants

Types, properties, and compatibility of lubricants used in refrigeration and air conditioning — from compressor oils to vacuum pump and cutting oils.

1.4.1 — Supporting Lubricants

Beyond compressor oils, technicians work with several other lubricants for ancillary equipment and fieldwork tasks. Each has its own selection criteria and handling requirements.

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Bearing Greases

Bearing greases are semi-solid lubricants used in applications where oil retention is critical and where sealed or shielded bearings are preferred.

Used in fan motors, pump bearings, and other rotating equipment related to refrigeration and air conditioning systems.
Selected based on temperature range, load, speed, and compatibility with seals and materials.

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Bearing Oils

Bearing oils are liquid lubricants used in bearings where continuous supply and circulation of oil are practical.

Common in larger motors, pumps, and industrial equipment.
Viscosity and additive package must match manufacturer requirements to provide proper film strength and protection.

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Cutting Oils

Cutting oils are used when drilling, tapping, threading, or machining piping and components.

Reduce friction and heat, improve surface finish, and extend tool life.
Technicians must ensure cutting oils do not contaminate refrigerant circuits.
Piping must be cleaned and deburred thoroughly before assembly and brazing.

1.4.2 — Refrigeration Oils

Refrigeration oils circulate with the refrigerant and must be compatible with both the refrigerant and system materials. They provide lubrication, sealing, and cooling for the compressor. Oil selection is critical — using the wrong oil type can cause compressor failure, system contamination, and loss of miscibility.

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Mineral Oil (MO)

Traditional petroleum-based oil. Used with CFC and many HCFC refrigerants (e.g., R-22). Not miscible with most HFCs.

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Alkyl Benzene (AB)

Synthetic oil for certain HCFC and HFC refrigerants. Better miscibility than mineral oil; improved oil return from low-temperature evaporators.

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Poly Vinyl Ether (PVE)

Synthetic oil for HFC and HFO refrigerants. Good miscibility and thermal stability. Moisture control remains important.

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PAG

Highly polar synthetic oil for automotive AC (especially R-134a). Excellent lubrication. Highly hygroscopic — keep containers sealed.

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PAO

Synthetic hydrocarbon for specialized applications. Good stability, low pour point, and favourable viscosity for extreme temperature ranges.

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POE

Most common oil for HFC and HFO systems. Excellent miscibility. Highly hygroscopic — strict moisture control and evacuation required.

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Mineral Oil (MO)

Mineral oil is a traditional lubricant refined from petroleum, used in many older systems.

Commonly used with CFC and many HCFC refrigerants such as R-22.
Not miscible enough with many HFCs — this limitation led to the development and use of synthetic oils such as POE.

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Alkyl Benzene (AB)

Alkyl benzene oils are synthetic lubricants used primarily with certain HCFC and HFC refrigerants.

Better miscibility with some refrigerants than mineral oils.
Improved stability and can help return oil from low-temperature evaporators.

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Poly Vinyl Ether (PVE)

PVE oils are synthetic lubricants used with certain HFC and HFO refrigerants, especially in some automotive and commercial applications.

Provide good miscibility and thermal stability.
Moisture control remains important, as with most synthetic refrigeration oils.

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Polyalkylene Glycol (PAG)

PAG oils are highly polar synthetic oils commonly used in automotive air conditioning systems, especially with R-134a.

Provide excellent lubrication characteristics in automotive compressors.
Highly hygroscopic — containers must be kept sealed to prevent moisture absorption.

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Polyalphaolefin (PAO)

PAO oils are synthetic hydrocarbons used in certain specialized refrigeration and compressor applications.

Offer good chemical stability, low pour point, and favourable viscosity characteristics.
May be selected for high- or low-temperature applications where mineral oils are inadequate.

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Polyol Ester (POE)

Most Common

POE oils are the most common lubricants used with HFC and many HFO refrigerants in stationary air conditioning and refrigeration systems.

Excellent miscibility with many HFCs supports effective oil return throughout the system.
Highly hygroscopic — absorbs moisture from air quickly. Containers and systems must be kept sealed.
Evacuation and dehydration procedures are critical when using POE oil.
More chemically active than mineral oils — cleanliness and proper filtration are essential.

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Hygroscopic Warning — POE & PAG

Both POE and PAG oils absorb moisture extremely rapidly when exposed to air. Always work quickly when opening containers, use only what is needed, and recap immediately. Moisture-contaminated oil can lead to acid formation, compressor damage, and copper plating inside the system.

1.4.3 — Vacuum Pump Oil

Vacuum pump oil is formulated specifically for deep vacuum service. It is not interchangeable with compressor oil or other lubricants.

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Vacuum Pump Oil

Change Regularly

Low vapour pressure allows the pump to achieve low micron levels without significant oil outgassing.
Oil must be changed regularly to remove moisture, acids, and contaminants picked up during evacuation.
Using contaminated or wrong-viscosity oil will prevent the pump from reaching the deep vacuum required for proper system preparation.

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Best Practice

Change vacuum pump oil before and after every heavy-duty evacuation, and any time the oil appears milky, dark, or shows visible contamination. Use only oil specified by the pump manufacturer to maintain rated performance.