Refrigerant oils are highly refined, non-foaming, low wax, low sulphur lubricants, refined to the highest possible levels of purity. The most common oil used in both R134a and R1234yf in today’s vehicles is PAG (based on polyalkalene glycol).

Refrigerant oils are specifically formulated for use in refrigeration and air conditioning systems. These are an important part of an airconditioning system and have been likened to blood in the human body. High quality oil is absolutely essential to the optimum performance of an airconditioning system. On the contrary, a low-quality oil can result in premature failure of components. Always ensure the correct grade of oil is used.


• To lubricate and control friction in moving parts such as the compressor and the TX valve.
• To assist in sealing (in the compressor shaft seal, the oil is the final seal between the carbon or
ceramic seal face and the compressor).
• To control corrosion.


• Refrigerant oil is hygroscopic (i.e. absorbs moisture) and should not be left open to atmosphere.

• Keep containers capped when not actually in use. Do not use oil that has been stored open for
more than 3 months.
• Refrigerant oils vary in grade, type and refrigerant compatibility. Do not mix oils.
• Never re-use refrigerant oil, or add old or contaminated oil to a system.
• Never mix a PAG and an Ester Oil.


• The oil content of an air conditioning compressor should always be checked:

a) at installation;
b) whenever the system is repaired;
c) Whenever a leak has occurred - especially leaks on the discharge, or ‘high’ side of the
• Use only the correct type and grade of oil for the compressor and refrigerant concerned.
• Check the correct quantity of oil required for the compressor concerned, and calculate the extra oil
required for larger systems. (For example, the recommended oil charge will not be sufficient for a
roof-top system with 6 metre hoses, or a split system with two evaporators.
• Do not overfill. An excessive overcharge of oil is as undesirable as an undercharge.