Development and Evaluation of Automotive Lubricating Oil from Jatropha curcas Oil

A Jatropha curcas-based bio-lubricant was developed and evaluated for automotive applications through acid esterification, base-catalyzed transesterification, in-situ peracetic acid epoxidation, and multi-additive blending. The molecular transformations were confirmed by GC–MS and FTIR, and physical properties were assessed using ASTM/ISO methods. Performance was further evaluated through a 12,000 km in-service motorcycle engine test and XRF wear analysis. Transesterification decreased kinematic viscosity at 40 °C from 36.6 to 16.7 cSt, and subsequent epoxidation and additive incorporation increased the viscosity to 47.2 cSt (40 °C) and 15.2 cSt (100 °C), meeting ISO VG-46 requirements. The resultant composition (JOA) showed density (888 kg m⁻³), viscosity index (227), pour point (−20 °C), flash point (230 °C), free fatty acid content (0.1%), and acid value < 0.5 mg KOH g⁻¹. The predominant components of JOA were determined by GC–MS, and ester and epoxide functionalities were confirmed by FTIR. During operation, the viscosity index decreased to 192.9, while maintaining acceptable viscosity retention and thermal stability. XRF analysis indicated controlled wear, with metal concentrations remaining within reported OEM guideline ranges. These results demonstrate the feasibility of using Jatropha curcas oil as a sustainable base stock for automotive lubricants.