Air conditioning compressors installed in automobiles require the use of strictly defined types of lubricants. Most air conditioners manufactured since 1996 have been using R134a refrigerant and need PAG (polyalkylene glycol) oil to lubricate the compressor mechanisms. Using the wrong refrigerant (compressor) oil or improper viscosity can damage the compressor itself. In most cases, the leading cause of damage to a new compressor is the use of inappropriate or inadequate refrigeration (compressor) oil.