Abstract: An apparatus and method determines and controls the oil level in one or more refrigeration system compressors. The invention returns lubricating oil to the compressors to maintain oil levels sufficient for proper lubrication of each compressor, and also monitors the flow rate of oil returned to each individual compressor. A level sensor and a flow control device are connected to a control circuit to control the flow of lubricating oil returning to the compressors. The control circuit controls the return flow of oil as well as various other functions of the system, monitors compressor oil levels, and determines the rate oil is returned to each compressor. The method includes measuring system parameters, comparing measured oil levels to desired oil levels, and injecting lubricating oil into a compressor if the measured oil level is below the desired level. The amount of oil added is then calculated and the oil flow rate is measured.