Exploring the lubrication mechanism of CeO2 nanoparticles dispersed in engine oil by bis(2-ethylhexyl) phosphate as a novel antiwear additive

Energy-efficient engine oils are required for sustainable transportation using vehicles, and oil companies aim to manufacture lube oils with more effective additives. Here we investigate the lubrication mechanism of cerium oxide (CeO2) nanoparticles dispersed in a fully synthetic engine oil (5 W-30) by bis(2-ethylhexyl) phosphate (HDEHP). Tribological tests were conducted using a tribometer based on ASTMG181 to mimic the ring-liner tribosystem environment. The results showed that the CeO2 nanolubricant enhanced the antifriction and antiwear characteristics of the rubbing surfaces by 12-21% and 62-80%, respectively, contrary to the results obtained with the 5 W-30 oil. In-depth field emission scanning electron microscope, energy dispersive spectrometer, and X-ray photoelectron spectrometry analyses of the worn surfaces after lubrication evidenced the production of a tribofilm, induced by physical adsorption and tribochemical reactions. Concisely, this study demonstrates the superior tribological performance of the CeO2 nanolubricant and provides insights for developing lube oils and improving the fuel economy in vehicle engines.