Compared with regular lubricants,the unique microstructures of ionic liquids (ILs) impart their lower viscous-pressure coefficients(VPC).By measuring film thickness via optical interferometry,the VPC value of an IL was obtained.The availability of the VPC value was confirmed through isothermal elastohydrodynamic lubrication (EHL) simulation.Using this VPC value,numerical simulations of thermoelastohydrodynamic lubrication (TEHL) of IL was conducted to analyze the film,temperature rise,friction coefficient and viscosity.The numerical results were compared with a common lubricating oil which has the same viscosity as the IL.The results show that IL has outstanding tribological properties compared with lubricating oil of the same viscosity,which is reflected in its very low temperature rise and friction coefficient in a wide range of speed and slip roll ratio,while the film thickness still remains more than 40% of the same viscous lubricating oil.The excellent TEHL properties of IL are mainly attributed to its low VPC.