Diesel engine oils for heavy duty vehicles in the Japanese market must have good total base number (TBN) retention, high load carrying capacity, and corrosion control in order to meet the requirements of the engine designs, valve train system and operating conditions. As a result, detergent type oils with high ash and low dispersancy are the preferred formulation approach. However, the use of multigrade oils combining high ash and high dispersancy is gradually increasing. This is in response to user demands for extended drain performance and improved fuel economy.This research institute has taken a leadership position by initiating a study to develop low sulfated ash type engine oils. Engine tests have been carried out to study the performance of low sulfated ash oils. The results from work to develop a low ash diesel engine oil suitable for the next generation heavy duty vehicles are also reported.