The Lowdown on Compressor Lubrication

The Lowdown on Compressor Lubrication

The most common lubricant used in automotive air conditioning systems is Polyalkylene Glycol oil, commonly known as Pag oil. Pag Oil is a synthetic oil used in A/C systems to lubricate the compressor and seals. The oil is extremely hygroscopic, conductive and is available in three viscosities, Pag 46, Pag 100 and Pag 150. The most commonly used is Pag 46.


Original compressor manufacturers dictate the correct oil type and amount required for the correct installation and best performance of the compressor.


Because the compressor comprises of moving mechanical components and runs at a high pressure and temperature, it is essential to make sure that the correct viscosity and quantity of Pag oil is used. 

One of the main reasons for a compressor to fail is due to incorrect lubrication. Mixing PAO oil with Pag oil will reduce lubrication of the internals of the compressor. Adding too much dye or other additives will also affect the lubrication effectiveness as this will dilute the Pag oil and have a detrimental effect on the compressor. When you flush the air conditioning system you should always ensure that all the flush fluid has been removed and that the system has been dried with OFN to make sure that the new oil being added to the system is not contaminated with flushing fluid still in the system.


Always follow the compressor or vehicle manufacturer guidelines for the right selection of the lubricant for the AC compressor.


Most if not all OEM compressors will come pre-filled with oil, but it is up to the person installing the compressor to check that the correct amount of oil is in the compressor.

When selecting your Pag oil, you should select a double end-capped PAG oil. The oil is chemically inactive and stable, offering exceptionally good lubrication characteristics, high moisture tolerance at high temperatures, and does not react chemically to form harmful acids/compounds.


·       When installing a new compressor, the installation instructions should be followed. To ensure that the compressor is lubricated correctly when it first engages, you should make sure that the correct amount and viscosity of oil is used. Once the compressor is filled with the correct oil, the front hub should be turned manually by hand to ensure that a thin film of oil covers the internal pistons and components of the compressor. By doing this, the compressor will be lubricated properly from cold thus avoiding any potential start-up damage occurring to the compressor.

·       Adding a universal oil to Pag oil may cause lubrication issues for the compressor as the universal oil will not mix properly with the Pag oil and will separate. This could expose the compressor to excessive friction and other components such as the seals and expansion valve to fail.


AP Air Europe stock a range of oils and dyes that are suitable for the R134a / R1234YF and Hybrid air conditioning systems and are OEM approved.

If you are in any doubt about which oil to use, call us on 01453 891320 for technical help and advice.

Service & support

Industry leading knowledge backed up with the best service available.

Daily shipping

All VOR goods are shipped in the UK on a next day AM service and with our carriers predict service you know when you will receive the parts.

New arrivals

AP Air have a large range of compressors, condensers and evaporators, which are expanding daily.


With over 30 years’ experience in the agricultural market you are in good hands at AP Air.

Heavy Off Road

Being distributors of Bergstrom, RedDot & MCC, the major players in this market we are your one stop shop.


With more trucks on the road AP Air are bringing our industry leading service to this market.


AP Air Ltd.

Unit 9 & 10 Wisloe Business Park
Wisloe Road
Cambridge, Glos, GL2 7AF
United Kingdom

P: +44 1453 891 320
F: +44 1453 549 647

Register your interest