Physicochemical Characteristics and Corrosion Resistance of Neopentyl Glycol Ester-Based Lubricant Blends

Modern industry’s increasing gasoline consumption underscores the importance of high-performance engine oils to minimize friction, wear, and heat generation. Anti-corrosion-based lubricants, particularly esters derived from biobased oils, are attracting attention for their low toxicity and high biodegradability. The present study explores the effect of commercial motor oil blending with a bio-lubricant, specifically Neopentyl Glycol (NPG) ester, synthesized from Calophyllum inophyllum oil. The synthesis of NPG ester was optimized to achieve complete conversion into long-chain tetra-esters. Blends were prepared by incorporating 5%, 10%, 15%, 20%, 25%, and 30% NPG ester into commercial lubricating oil (CLO). Physicochemical properties such as Foaming Test and Stability, Pour Point of Petroleum Products, Total Acid Number (TAN) and Total Base Number (TBN), Kinematic Viscosity (KV), and Viscosity Index (VI), Copper Strip Corrosion Test, High-Temperature High-Shear (HTHS) Viscosity, Cold Cranking and Low-Temperature Pumping Viscosity were evaluated to determine the optimal ratio. Among the tested blends, CLO + 15% NPG ester exhibited the best overall performance, demonstrating superior viscosity stability, improved thermal resistance, and enhanced lubricity without compromising other key properties. Blends above 20% showed a decline in performance, likely due to phase incompatibility and oxidative susceptibility. The findings suggest that CLO + 15% NPG ester represents an optimal balance between improved lubrication performance and environmental benefits, making it a promising candidate for partially replacing mineral oil in automotive applications while reducing environmental impact.