Development of energy-efficient lubricants is a way to reduce energy consumption for transportation, with the tendency to design molecules that are beneficial in reducing the viscosity of synthetic oils. Oligoether esters (OEEs), as a low-viscosity ester base oil, have characteristics such as simple synthesis and excellent lubrication effect; however, the application of OEEs in tribology field has rarely been investigated. The objective of the present study is to investigate the effect of structure on the lubricating performance of OEEs and to develop a predictive model for OEEs based on quantitative structure‒property relationship (QSPR) through a combination of experiment and statistical modeling. Results showed that glycol chains contribute positively to lubrication with the ether functional groups increasing the sites of adsorption. Compared to branched-chain OEEs, straight-chain OEEs exhibited reduced wear, which was mainly due to the thicker adsorption film formed by the straight-chain structure. Furthermore, carbon films were detected on lightly worn surfaces, indicating that OEEs underwent oxidation during the friction process. Based on the results of principal component analysis (PCA) and partial least squares (PLS), it could be found that the predictive models of viscosity‒temperature performance, thermal stability performance, coefficient of friction (COF), and wear volume (WV) performed well and robustly. Among them, COF and WV can be best predicted with an R² of about 0.90.

The depletion of petroleum resources and the intensification of environmental problems have necessitated the development of renewable products from bio-based chemicals instead of petroleum resources. Herein, a new kind of ester lubricating oil, isooctyl furan dicarboxylate (isooctyl-FD), was prepared from bio-based 2, 5-furandicarboxylic acid. The structure of isooctyl-FD was evaluated using nuclear magnetic resonance imaging and high-resolution mass spectroscopy. Its physicochemical and tribological properties including thermal and oxidation stabilities, flash point and pour point, viscosity and viscosity index, and friction-reducing and anti-wear properties were systematically evaluated. The results show that isooctyl-FD has comparable thermal and oxidation stability to the synthetic ester lubricating oil, isooctyl sebacate (isooctyl-S). Its friction-reducing and anti-wear properties are superior to isooctyl-S; however, its viscosity-temperature and low-temperature properties are inferior to isooctyl-S.