Analysis of Deposit Formation Mechanism on TEOST 33C by Engine Oil Containing MoDTC 2008-01-2480

The addition of molybdenum dithiocarbamate (MoDTC) to engine oil improves the fuel consumption of vehicles. However, this is also widely known to cause deposit accretion in the Thermo-Oxidation Engine Oil Simulation Test (TEOST 33C). Thus the effects of additives on TEOST 33C and elemental analysis of the deposits were evaluated to analyze the deposit formation mechanism in TEOST 33C by engine oil containing MoDTC. An elemental analysis of deposits revealed that most consisted of carbide and contained small amounts of molybdenum compounds. Deposit accretion was not caused due to the remarkable increase of compounds derived from MoDTC. It was assumed that they acted as a decomposition catalyst under high temperature and induced carbide to be deposited.