CONTAMINATION OF MARINE CRANKCASE LUBRICANTS BY RAW FUEL - CONSEQUENCES, AND METHODS OF DETECTION

In the late 1980s, operators of trunk-piston marine engines encountere d the problem of contamination of engine lubricating oils by fuel. Thi s paper summarises the results of two surveys conducted by CEC IL-047, with cooperation from members of the CIMAC Lubricants Working Group a nd the Marine Engineering Society of Japan. The surveys ascertained th e frequency and severity of problems in trunk-piston engines that aros e either from contamination of crankcase oil by raw fuel or from inter actions between the oil and combustion products. It was found that alt hough contamination was most prevalent in the camshaft housing and the crankcase, the greatest impact on engine operation came from deposits on the fuel-pump plunger and on piston undercrowns. In parallel, a su rvey and a critical review were conducted of currently available analy tical methods used for detecting the contamination of lubricants by ma rine residual fuel. It appears that there is no standard simple, relia ble, accurate and cheap method of detecting contamination of trunk-pis ton engine lubricants by fuel. The interpretation of results from exis ting macro-or micro-analytical methods is limited by the varied charac teristics of the fuels in use, and by the changes that take place in b oth fuels and lubricants during service.