We have a chiller that has Carrier O6D compressors. A technician replaced drier cores and changed oil. He used C4 instead of C3 which I know is the right oil. C4 was used more in R12,11,113 applications. There is nothing special about this chiller,R22 process chilled water. Can someone shed some light on this? I'm afraid of wax build up and poor oil return.