The lubricating system of a small turboprop engine is described in terms of capacity, temperatures, type of lubrication, material of oil-wetted parts, system routing, and problem areas. The customer's installation and parent lubricating system are described and their importance discussed. A discussion of the SOAP analysis procedure is presented with reference to the sampling interval, interpretation of data, and a history of selected impending failures. The use of SOAP analysis to allow replacement of marginal design parts is discussed. The necessity to monitor engine lubricating systems during engine development is emphasized.