Microbial degradation of marine lubricating oils

OVER the past two years, ten vessels on intercontinental routes have been examined and found to have suffered varying degrees of microbiological deterioration of the main engine lubricating oil. In one case, the emulsification of the oil had caused severe corrosion, necessitating a crankshaft regrind. In several cases the oil was unsuitable for further use and had to be discarded. The paper briefly outlines the mechanism of oil degradation by micro‐organisms and reports practical experience of the types and origin of organisms found in affected ships and the appearance of the oil and bearing surfaces suffering this form of attack. Practical recommendations are given for identification of the problem at the early stages and tested methods used to eliminate the bacterial infection are discussed.