Compatibility of Engine Oil Viscosity Improver and Biodiesel Fatty Acid Methyl Ester

Abstract

The present work focused on the compatibility of a popular engine oil viscosity improver polymethacrylate (PMA) and a biodiesel fatty acid methyl ester methyl oleate (MO). Thermal oxidation operations of blends of PMA, MO and a mineral base oil were performed for evaluating the interactions between PMA and MO. The viscosity and viscosity index of fresh and oxidized blends were determined and calculated. Thereafter the chemical compositions of oxidized blends were characterized by a gas chromatography coupled to a mass spectrometer. Results showed that viscosities of the blends increased after oxidation, and the increases in viscosity after oxidation for blends containing MO were greater than those for blends without MO. Furthermore, PMA was substantially efficient in improving viscosity index of both fresh and oxidized blends with and without MO, although viscosity index of blends slightly declined with increasing concentrations of MO in a blend. Finally, chemical species of methacrylates were generated in the oxidation processes of blends, despite whether or not there was MO in the blends. The present results preliminarily demonstrated that direct chemical interactions between PMA and MO were unobvious, and confirmed that PMA was well compatible with MO in viscosity index improvement.