The deposition of ash derived from engine oil on the surface of diesel particle filters (DPF) has recently been reported to degrade the performance of the DPF. It is generally known that phosphorus in engine oil is adsorbed on the surface of an automotive exhaust catalyst, reducing the performance of the catalyst. Thus, the amounts of ash and phosphorus in engine oil have been decreased. We have developed a non-phosphorus, non-ash engine oil (NPNA) that does not contain metal-based detergents or zinc dialkyldithiophosphate (ZnDTP). Various engine tests were performed, and we confirmed that under normal running conditions, the NPNA oil had a sufficiently high piston detergency and wear resistance-two important requirements for engine oil-to meet current American and Japanese standards.
However, the piston detergency of NPNA required further improvement when engine running conditions were more severe. We performed a hot tube test to evaluate the piston detergency of NPNA at high temperatures and developed additives (ashless detergents) that did not contain ash (metallic elements). We then evaluated the piston detergency and valve train wear prevention of the improved NPNA. The tests were performed using two engines: one manufactured by Caterpillar Inc. and regulated by the guidelines of the American Society for Testing and Materials (ASTM) D6750, and one manufactured by Hino Motors, Ltd. and regulated by the Japanese Automotive Standards Organization (JASO) M354:2015. We confirmed that the improved NPNA possessed excellent piston detergency and provided outstanding valve train wear prevention.