Differences between the various oils for air conditioning compressors
PAG oil is usually used in belt-driven air conditioning compressors with viscosities ISO 46, ISO 100 or ISO 150. Polyalkylene glycol (PAG) based oils are transparent and hygroscopic (attract water). Water in the oil-R134a refrigerant mixture leads to the formation of acids and sludge and can damage the compressor. R1234yf, on the other hand, is particularly sensitive, which is why no PAG should be used here. Therefore, the correct handling of the oil is particularly important. They may only be exposed to the ambient air for a very short time. Storage must take place in a vapour-tight aluminum container and after opening a container, the PAG must be used up quickly (within 4-6 weeks for regular aluminum containers)
PAO-ÖL, like PAG, is a synthetically produced oil that is usually offered with a viscosity of ISO 68 as a universal oil for air conditioning compressors. It is not hygroscopic and is therefore particularly suitable for R1234yf systems. Caution: PAO is not miscible with PAG oil.
POE oil: Polyester oil or ester-based oil has the property of being electrically insulating. For this reason, various (not all) car manufacturers use it as a lubricant for electric air conditioning compressors in hybrid vehicles. If no electrically insulating oil is used here and there are insulation defects in the electrical components inside the compressor, electrical hazards can arise because high voltage is transmitted to the compressor housing.