Lube Formulation Effects on Transfer of Elements to Exhaust After-Treatment System Components

After-treatment systems (ATS) consisting of new catalyst technologies and particulate filters will be necessary to meet increasingly stringent global regulations limiting particulate matter (PM) and NOx emissions from heavy duty and light duty diesel vehicles. Fuels and lubes contain elements such as sulfur, phosphorus and ash-forming metals that can adversely impact the efficiency and durability of these systems.

Investigations of the impact of lubricant formulation on the transfer of ash-forming elements to diesel particulate filters (DPF) and transfer of sulfur to NOx storage catalysts were conducted using passenger car diesel engine technology. It was observed that for ATS configurations with catalyst(s) upstream of the DPF, transfer of ash-forming elements to the DPF was significantly lower than expected on the basis of oil consumption and lube composition. Sulfur transfer strongly correlated with oil consumption and lubricant sulfur content. Differences in volatility or stability of various sulfur-containing lube components were illustrated in bench volatility tests. However, these differences were not discernable under the engine operating conditions defined in this study. An ATS-compatible lubricant technology with acceptable engine wear protection and deposit control was developed. Its potential to reduce DPF ash deposits was proven in engine and vehicle tests.