Experimental investigation of effect of biodiesel fatty acid methyl ester on performance of engine oil dispersant additive

In the present work, blends of methyl oleate (MO), polyisobutylene-bis-succinimide (PIBSI) and a mineral lubricant base oil were oxidized and some of their physicochemical properties were evaluated to understand the effects of biodiesel fatty acid methyl esters on the performance of the engine oil dispersant additive PIBSI. The oxidation experimentations of blends were conducted under elevated temperatures. Thereafter, the viscosity and acidity of fresh and oxidized blends were determined. The dispersancy, thermal stability and chemical species of oxidized samples were tested and analyzed by the blotter spot method, a TGA, and a GC/MS, respectively. Results showed that the viscosity and acidity of blends containing MO increased significantly after oxidation. The dispersing ability of PIBSI was markedly impaired by only a small amount of MO in a blend. In addition, the thermal characteristics of blends were altered by MO. Many varieties of oxygenated chemicals in the oxidized blend containing MO were detected. The negative impact of MO on performances of PIBSI was attributed to the accelerated oxidation caused by MO, and to the chemical interactions between MO and PIBSI. The present results demonstrated that PIBSI was incompatible with MO.