ABSTRACT

A study was carried out on the stability to microbial deterioration of car engine lubricating oil. Six samples which were classified into used and unused oil were employed. The used oil samples were collected from five kinds of' vehicles namely. Peugeot(504), Japanese(Toyota), Luxurious bus(Marcopolo), Mitsubishi bus, Mercedes Benz(flat boot) Car. The predominant bacterial species were the Bacillus, Actinoinyces and Corynebacieriuin. While the fungal species in order of predominance in all samples includes Aspergillus, cladosporiun 1, Ceplialosporiuin and Pen icilluin species; The growth of the fuiigal organisms and bacterial organisms at different temperatures states and their utilization of' the oil indicated the ability of these organisms to proliferate in the oil as well as to utilize the carbon content of the oil as their sole energy source. Also ,the results showed that lubricating oil in service is more prone io biodeterioi'ation than unused oil. The biodeteriogenic potentials of these organisms caused changes of various sorts in the quality and hence performance of' the oil.