Comprehensive evaluation of canola oil with natural additives for hydraulic applications: tribological, rheological and contact angle measurements

Purpose This study aims to evaluate the tribological performance of canola oil-based hydraulic fluids of viscosity grade 32 (ISO VG32), enhanced with natural antioxidants – eugenol, curcumin and ascorbic acid. Design/methodology/approach The formulations were prepared with 0.5 wt.% of each additive and benchmarked against a commercial mineral ISO VG32 oil. Physical properties (density, viscosity, viscosity index), tribological behavior (friction coefficient, wear rate, lubricant efficiency), wettability and the lubricant’s final condition after friction tests were analyzed using standardized ASTM methodologies. Findings Results revealed that vegetable-based formulations exhibited higher viscosity indices (up to 41% higher than mineral oil), thereby improving stability under temperature variations. Tribological tests demonstrated lower friction coefficients and enhanced lubricant efficiency compared to mineral oil, with the canola oil/ascorbic acid blend showing the most favorable performance (friction reduction of 43% and wear rate reduction of 99%). Contact angle analysis confirmed cohesive molecular behavior. Originality/value The incorporation of natural antioxidants significantly improved the oxidative and tribological stability of canola oil, positioning these bio-lubricants as eco-friendly, high-performance alternatives to mineral hydraulic fluids. Only a few researchers evaluate the influence of additives on wettability and explore their impact on the tribological behavior in bio-hydraulic formulations.