Eco-grease from upcycling of waste oils: a formulation study for high-performance lubricants

Abstract The disposal of waste oils, particularly waste engine oil (WEO) and waste turbine oil (WTO), presents serious economic and environmental issues due to their high contamination and degradation levels, which reduce the efficiency of direct reuse or conventional recycling. This study investigates a practical approach for upcycling WTO and WEO into high-performance lubricating grease, providing a sustainable substitute for petroleum-based lubricants. The study includes five essential stages: waste oil collection, pre-treatment, characterization, grease formulation, and performance assessment. Following treatment, the viscosity, elemental content, and moisture levels of the oils complied with Department of Environment (DOE) and ASTM D5185 standards, confirming their viability as base oils. The formulated greases achieved NLGI grades of 2–3, oil bleed percentages within a ± 15%, and oil separation below 4%. They also exhibited low coefficients of friction (0.062–0.133) and wear scar diameters ranging from 415.65 to 866 μm. These results confirm that treated WTO and WEO can be converted into greases with performance comparable to conventional products, supporting reduced dependence on virgin base oils. The formulations were assessed under relevant ASTM and NLGI standards. Future work may explore additives or scale-up approaches to enhance long-term performance and market readiness.