The compressor has moving parts internally which need to be lubricated. Like an engine, most AC compressors use a system with pistons. Without PAG oil, you'd have metal-on-metal contact, and the pistons would end up seizing.
mineral oil
Compressor oil is a specialized lubricant designed for use in air compressors and refrigeration systems. It helps reduce friction between moving parts, enhances efficiency, and prevents wear and tear. Additionally, it plays a crucial role in dissipating heat and protecting against rust and corrosion. The formulation of compressor oil can vary depending on the type of compressor and its intended application, including synthetic and mineral oil options.
Floc in refrigeration oil is wax that has separated out from oil containing parathene.
Absolutely not. Use whatever the manufacturer recommends, AMS 2-stroke oil, or Klotz R50. Only use oil with castor oil if you run it very hard on a daily basis.
All 134a Refrigeration systems use polyester oil. You'll need to find polester oil for automobiles.
Oil
Polyester (POE) Oil
What is the Material compatibility in relation to refrigeration oils?
There are different types of refrigerant oils. Refrigerants such as R22 and R12 usually use mineral oil. But some of blended refrigerants like R410A can sometimes use a poly oil. These oils can not be blended together. So a system that already has a refrigerant with mineral oil must be charged with refrigerants with the same oil.
Oil in a AC compressor is there so that the mechanical parts don't over heat from friction
To return oil to the compressor.
The compressor oil