Fully synthetic refrigeration oils based on synthetic polyolesters – especially suitable for non-ozone depleting FC/HFC refrigerants, such as R134a, R404A, R507, R410A, R407C. Also suitable for hydrocarbon refrigerants. As polyolester oils strongly tend to absorb water (hygroscopic behavior), the contact of these lubricants with air (atmospheric humidity) has to be limited to a minimum.