Chemical and kinetic insights into fuel lubricity loss of low-sulfur diesel upon the addition of multiple oxygenated compounds

Abstract Fatty acid methyl esters (FAMEs, the primary components of biodiesel) have been proven to improve the fuel lubricity of low-sulfur diesel (LSD); however, fuel lubricity performances associated with non-conventional biodiesels (short-chain FAMEs) were rarely discussed. Additionally, the complex lubricity behavior with FAMEs containing free fatty acids or antioxidants is unknown. Our results showed that lauric acid methyl ester brings limited fuel lubricity improvement to LSD. The presence of fatty acids and antioxidants facilitated the formation of different frictional products on wear tracks or eliminated wear-resistive products. We further interpret the resulted fuel lubricities by resolving kinetic features of measured electrical contact resistances and chemical composition profiles within wear tracks from standardized tests. Beyond understanding how oxygenated compounds affect fuel lubricity, we expect robust analytical approaches demonstrated in this work to shed light on more fuel lubricity problems upon the formulation of multiple species.