▎ 摘　　要

The present work concentrate on the improvement in physico-chemical, and tribological properties of used engine oil using graphene nanoparticles. The used engine oil (15W40) has been collected from heavy earth moving machines (HEMM) of coal mines. The graphene nanoparticles have been used for the preparation of nanolubricants and the properties are compared with unused oil. Kinematic viscosity, viscosity index (VI) and density have been measured to examine the physico-chemical properties of nanolubricants and observe the improvements. The stable chemical structure of nanolubricants has been found with Fourier transform infrared spectroscopy (FTIR). The performance of nanolubricant has been found by measuring wear and friction coefficient between grey cast iron contacts and observed the significant reduction in wear and friction compared to used oil. The same has been validated by measuring the wear scar with the help of optical microscopy and electron dispersive X-ray spectroscopy. The life of the used oil has been enhanced with the addition of nanoparticles.