Predicting Retention of Fuel Economy Benefits in Engine Oils Containing Soluble Molybdenum-Type Friction Modifiers

In the field, it is observed that molybdenum containing fuel economy engine oils lose their friction reduction capabilities over extended periods of use. In Sequence VI engine tests, an aging stage is included in which oil is aged within the engine before evaluation of fuel economy. The efficacy of friction modifiers containing oils is currently estimated in a laboratory on a linear reciprocating friction tester. This study deals with a laboratory study to predict the effect of aging on the long-term fuel economy of friction modifiers containing engine oils based on the retention of its coefficient of friction values. The aging of the oil sample in the laboratory was achieved through an oxidation test. Aging in the field was carried out in a field trial. The aged samples were evaluated on the friction tester to determine the coefficient of friction and the wear scar diameter. Three friction modifiers containing oils were evaluated in the field. The study shows that the aging effect can be predicted in laboratory-scale bench tests and that the results correlate well with field performance.