Refrigeration circuit for vehicular air conditioning systems

A vehicular air conditioning system (10) includes a compressor (110) having a crank chamber (138), a suction chamber (120), and a discharge chamber (122). A refrigerant mixture includes carbon dioxide and oil. A conduit (13) connects the discharge chamber (122) of the compressor (110) directly with an oil separator (14) to route the refrigerant mixture directly to the oil separator (14). A capillary tube (16) is connected between the oil separator (14) and the crank chamber (138) of the compressor (110) to cool and throttle oil enroute directly to the crank chamber (138) of the compressor (110).