Role of selected dispersants in gasoline particulate emissions under lubricant formulations in the presence of commercial package and dispersant additives: Its effect on emissions, viscosity, and soot morphology

Abstract

The aim of this study was to investigate regulated and unregulated emissions including particulates generated from a gasoline direct injection engine with different oil formulations. Lubricating oil analysis was also performed with focusing on both viscosity and soot-in-oil morphology. According to the Euro-6 regulation, the standard for particle mass emissions of a gasoline engine is 0.005 g/km (6.0× 1011 N/km for particle number). Lubricant oil accounts for a considerable fraction of the particulate volatile fraction. In this study, intentional oil consumption together with different compositions of additives were investigated based on engine dynamometer tests. Regulated (PM, THC) and unregulated (VOCs) emissions were measured corresponding to the different level (baseline, Disp-1.5, Disp-3.0 and Wear-1.5) in lubricant additive formulations. Subsequently, the role of dispersant additives was observed and discussed in terms of additive interaction. Among the test cases, viscosity difference were distinctively observed both in fresh oil and soot (carbon black) containing oil. Higher dispersant level yielded an increase in viscosity of bulk oil, which is consistent with the previous study reported regarding diesel engines. Soot-in-oil morphology was also studied focused on the difference from diesel. The associated higher viscosity of the lubricating oil (Disp-3.0) is considered to yield more inhomogeneity of air-fuel mixtures, which finally results in more soot mass relative to Disp-1.5. engine cases.