Refrigeration cycle comprising in the direction of flow of a circulating refrigerant: a compressor unit; an oil separation device (4, 5) which is configured for separating oil from a refrigerant-oil-mixture leaving the compressor unit; at least one gas cooler/condenser; at least one expansion device; and at least one evaporator; wherein the oil separation device (4, 5) comprises: a refrigerant inlet line connected to the compressor unit, the refrigerant inlet line having at least a first portion with a first diameter; a refrigerant conduit arranged downstream of and connected to the refrigerant inlet line, the refrigerant conduit having at least a second portion with a second diameter, which is larger than the first diameter; a refrigerant outlet line arranged downstream of and connected to the refrigerant conduit, the refrigerant outlet line having at least a third portion with a third diameter, which is smaller than the second diameter; wherein the third portion having the third diameter extends into the second portion forming an oil separation pocket between the outer diameter of the third portion and the inner diameter of the second portion; and an oil suction line having an inlet portion which opens into the second portion and is configured for receiving oil from the second portion and having an outlet portion; characterized in that the refrigeration cycle further comprises a switchable valve arranged between the inlet portion and the outlet portion of the oil suction line and; a control unit which is configured for controlling the switchable valve based on at least one of the level of oil within the suction line's inlet portion, the oil differential pressure and/or on the level of oil within at least one of the compressors (2a, 2b, 2c). a compressor unit; an oil separation device (4, 5) which is configured for separating oil from a refrigerant-oil-mixture leaving the compressor unit; at least one gas cooler/condenser; at least one expansion device; and at least one evaporator; a refrigerant inlet line connected to the compressor unit, the refrigerant inlet line having at least a first portion with a first diameter; a refrigerant conduit arranged downstream of and connected to the refrigerant inlet line, the refrigerant conduit having at least a second portion with a second diameter, which is larger than the first diameter; a refrigerant outlet line arranged downstream of and connected to the refrigerant conduit, the refrigerant outlet line having at least a third portion with a third diameter, which is smaller than the second diameter; wherein the third portion having the third diameter extends into the second portion forming an oil separation pocket between the outer diameter of the third portion and the inner diameter of the second portion; and an oil suction line having an inlet portion which opens into the second portion and is configured for receiving oil from the second portion and having an outlet portion; characterized in that the refrigeration cycle further comprises a switchable valve arranged between the inlet portion and the outlet portion of the oil suction line and; a control unit which is configured for controlling the switchable valve based on at least one of the level of oil within the suction line's inlet portion, the oil differential pressure and/or on the level of oil within at least one of the compressors (2a, 2b, 2c). a switchable valve arranged between the inlet portion and the outlet portion of the oil suction line and; a control unit which is configured for controlling the switchable valve based on at least one of the level of oil within the suction line's inlet portion, the oil differential pressure and/or on the level of oil within at least one of the compressors (2a, 2b, 2c).