Abstract: Herein disclosed is a lubricant oil or lubricant for the compressor of a refrigeration system which operates with a refrigerant comprising at least one component of the hydrocarbon (HC) group of refrigerants, (a) whereby the lubricant consists of at least 85 weight % of alkylbenzene having an average molecular weight of ?160 g/mol and exhibiting a viscosity of 2.2-3.0 centistokes (cSt) at 40 deg C.; optionally wherein the alkylbenzene consists of at least 85 wt % of linear (straight chain) alkylbenzene, having an average molecular weight of ?160 g/mol and exhibiting a viscosity of 2.2-3.0 centistokes (cSt) at 40 deg C.; (b) or alternatively whereby the lubricant consists of at least 85 weight % of alkylbenzene having an average molecular weight of ?190 g/mol and having a viscosity of 2.5-3.5 cSt at 40 deg C.; optionally wherein the alkylbenzene consists of at least 85 wt % of linear (straight chain) alkylbenzene, having an average molecular weight of ?190 g/mol and exhibiting a viscosity of 2.5-3.