Abstract: Oil separation for a horizontal refrigeration screw compressor is achieved in a series of steps which achieves nearly oil-free refrigerant gas. The refrigerant is discharged from the compressor into a generally cylindrical shell which is divided into three chambers. A generally horizontal, but slightly tilted, divider plate unequally divides the cylindrical shell into two chambers for the greater portion of the cylindrical shell. A cylindrical chamber at the end of the cylindrical shell provides fluid communication between the other two chambers. The compressor discharge is located in the lower and larger chamber which is a segment of a circle portion which also contains the oil sump. A discharge deflector turns the compressor discharge flow at least 90.degree., but as much as 135.degree., and causes it to impact upon the lower surface of the divider plate and depositing oil thereon. The flow striking the divider plate is deflected 180.degree. and is caused to turn approximately 90.degree.