Biodiesel Promotes Iron-Catalyzed Oxidation of Engine Lubricating Oil

The growing trend of increasing biodiesel concentrations in diesel fuel blends has led to concerns about its effect on the oxidation of formulated oils within internal combustion engines. We observe that biodiesel is not only susceptible to rapid oxidation at elevated temperatures but is also responsible for acceleration of the oxidation process of the lubricant base oil when in the presence of soluble iron; this is supported by a range of control and model experiments. A mixture of oxidized biodiesel and Fe­(III) leads to the formation of catalytic iron carboxylate networks that remain solubilized, as observed by UV–Vis and infrared absorption studies. These observations are important for the fundamental understanding of the chemistry within industry standard laboratory bench tests for lubricant oil formulations and can aid the design of new lubricants with improved biodiesel compatibility. Such lubricants have the potential for a reduced carbon footprint via waste reduction.