The function of the compressor oil is to lubricate the moving parts in the compressor. The oil film also keeps the rubber seals in the refrigerant lines and connections supple and reduces diffusion.
To ensure perfect operation, it is important to use just the right amount of compressor oil. If less than the recommended amount is used, this will have the following consequence
Overfilling with lubricant can however also impair cooling action. Genuine OEM compressors are filled at the factory with the total amount of oil of the correct viscosity and type required for the refrigerant circuit.
The compressor oil is mixed with the refrigerant and flows around the refrigerant circuit.
Compressor oils differ greatly: As a general rule, use should only be made of the oil specified by the vehicle or compressor manufacturer. The corresponding information can normally be found on the compressor rating plate. A special, non-conductive compressor oil is usually required for hybrid vehicles and air conditioners with an electric compressor.