Audi A4 Owners & Service Manuals

Audi A4: Refrigerant Oil

General Information


When handling refrigerant oil, pay attention to local regulations.

Refrigerant oil mixes with the refrigerant (about 20-40%, depending on compressor type and amount of refrigerant) and circulates constantly in the system, lubricating the moving parts.

Special synthetic refrigerant oils, for example polyalkylene glycol (PAG) oil, are used in conjunction with R134a air conditioning systems. This is necessary as mineral oil, for example, does not mix with R134a. In addition, the materials of the R134a air conditioning system could be corroded as a result of mixture flowing through the refrigerant circuit under pressure at high temperatures or breakdown of the lubricating film in the compressor. Using non-approved oils can cause the HVAC system to malfunction. Only use approved oils.

Refer to the Parts Catalog.

Type of oil for R134a in motor vehicles: PAG. (Polyalkyleneglycol)


  • Do not store open containers of refrigerant oil because it attracts moisture.
  • Always keep oil containers sealed.
  • Do not use old refrigerant oil over again. For disposing refrigerant oil of unknown origin pay attention to local regulations.
  • Ester-based oils are only intended for use in large systems at this time, not in passenger vehicle systems.

Refrigerant Oil Characteristics

The most important properties are a high degree of solubility with refrigerant, good lubricity, absence of acid and minimal water content. Only certain oils are permitted. For a list of approved refrigerant oils and capacities. Refer to → Chapter "Approved Refrigerant Oils and Capacities".

PAG oils, which are appropriate for refrigerant R134a, are highly hygroscopic and do not mix with other oils. Opened containers should therefore be closed again immediately to prevent ingress of moisture. Moisture and acids promote aging of refrigerant oil, causing it to become dark and viscous as well as corrosive towards metals.


  • Refrigerant oil, because of its chemical properties, must not be disposed of with engine oils or transmission oils. For disposing refrigerant oil of unknown origin pay attention to local regulations.
  • Only the oil approved for the A/C compressor may be used in refrigerant circuits with refrigerant R134a. For the correct oil. Refer to the Parts Catalog. For the correct capacities. Refer to → Chapter "Approved Refrigerant Oils and Capacities".


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