Compressor oil lubricates moving parts and circulates to a small extent with the refrigerant.
Compatibility
Every refrigerant requires a specific type of lubricant with suitable chemical and thermodynamic behavior.
Wrong oil
It can cause insufficient lubrication, oil return problems, or chemical incompatibility.
Moisture
Certain modern lubricants are hygroscopic and absorb moisture from the air.
Service
Use only the lubricant specified by the manufacturer of the compressor and the unit.