Effect of Zinc Dialkyl Dithiophosphate (ZDDP) Additive on the Physicochemical Characteristics of Neem Oil-Based Bio-Lubricants

This study investigates the effects of Zinc Dialkyl Dithiophosphate (ZDDP) additive on selected physico-chemical properties of neem oil bio-lubricant. Raw neem oil transesterified into bio-lubricant ester, was prepared as a base formulation and amended with ZDDP at concentrations of 1%, 2%, and 3% (w/w). The properties evaluated included density, specific gravity, kinematic viscosity, acid value, free fatty acid (FFA) content, saponification value, pour point, cloud point, and flash point. Experimental results show that increasing ZDDP concentration slightly reduced density and specific gravity while producing a gradual increase in viscosity. Acid value and free fatty acids decreased marginally with higher ZDDP loading. Saponification value increased slightly across the additive concentrations. Cold-flow properties improved modestly, as evidenced by lowered pour and cloud points. Flash point increased with ZDDP addition, suggesting enhanced thermal safety. Overall, ZDDP positively influenced multiple physico-chemical indicators relevant to engine-oil suitability, although the specific tribological performance and wear protection require further evaluation through wear and oxidation tests.