An investigation of the relationship between used engine oil properties and simulated intake valve deposits

The degradation of engine oil and its influence on the formation of intake valve deposits is being discussed in this paper. Degraded samples of oil were prepared using a stationary engine testbed while deposition studies were performed using a bench top simulator. The degree of degradation, as indicated by the amount of polymeric, oxidized and oxidative products, increases as the engine oil is used over a period of time. The rate of degradation, however, varies depending on the quality of base oil and the type of additives used. It was observed that the degraded oil played an important role in the formation of inlet valve deposits.