Fully synthetic, polyalkylene glycol (PAG)-based oil which is used for the lubrication, sealing and cooling of refrigerant compressors or refrigerant circuits in passenger or commercial vehicle air conditioning systems. It has been formulated so that it can be mixed with type R134a refrigerants and is therefore outstandingly suitable for this purpose. The oil is hygroscopic and absorbs moisture from the ambient air; it is therefore filled under nitrogen. It meets the requirements of standard refrigerant compressor and refrigeration system manufacturers. Leaks can be detected quickly using a UV lamp thanks to the yellow fluorescent color.