Valorisation of non-edible and waste cooking oils into hybrid biolubricants: A tribological study

The use of non-edible oils and waste cooking oil as a biolubricant production feedstock can provide a promising and environmentally sound alternative to the current petroleum-based lubricants. The objective of this study was to produce and test biolubricant blends using Calophyllum inophyllum oil and waste cooking oil through esterification, transesterification, and trimethylpropane (TMP) ester reactions. The biolubricant blends produced in this study, denoted as CIWBL ( Calophyllum inophyllum and waste cooking oil biolubricant), had properties equivalent to commercial SAE 15W40 lubricants. The CIWBL had kinematic viscosities of 35.46 mm²/s and 6.02 mm²/s, and viscosity index of 115.3 and flash point of 289.2 °C at 40 °C and 100 °C, respectively; these exceeded the minimum required specifications of ISO VG 32 and 46 viscosity grades. The tribological test revealed that the presence of CIWBL was effective in lowering the friction coefficient and wear values compared with those of the commercially available lubricants. The best performance among all the CIWBL formulations was displayed by CIWBL40, which indicated the lowest friction coefficient (0.0336) and smallest wear scar diameter (350 μm). This is due to balanced viscosity and strong biolubricant film formation. On the contrary, the presence of CIWBL in high proportions led to increased wear values because of the excessive amount of biolubricants. The CIWBL concentration between 30 % and 50 % could be the best alternative to be applied as environmentally friendly lubricant additive in hydraulic, machine, and automotive lubricant applications. • Valorisation of waste oils offers eco-friendly biolubricants for industry use. • Modified oils achieved viscosity index 115.3 and flash point 289.2 °C. • Biolubricant blends reduced friction compared with commercial lubricant. • CIWBL40 blend gave lowest friction coefficient and smallest wear scar. • Optimal blends 30–50 % CIWBL improved tribological performance.