Ricinoleate anion based ionic liquids (ILs) were synthesized from four different nitrogen containing cationic counterparts such as tetrabutylammonium, tetrapropylammonium, cetyltrimethylammonium, imidazolium and evaluated for tribological performance in two lubricant base stocks. From the tribological tests it was found that the synthesized ILs in base oil significantly reduced the wear scar diameter by 17-25 % and a remarkable reduction in wear observed for all the tested load and rotation speed at optimized concentration and also improved the load carrying capacity by 25-43%. The results conclude that the cation present in IL control the thermal stability, antiwear and extreme pressure properties. The imidazolium cation containing IL showed the better performance among all the ILs being studied. Additionally, the morphology of worn surface and deposition of elementals on rubbed surface lubricated with base oil and base oil containing IL was studied by scanning electron microscope (SEM) and Energy-dispersive X-ray spectroscopy (EDX). The fatty acid constituted ILs are promising immense efficiency as environmentally friendly and renewable lubricant additives since they are free from halide, sulphate and phosphate ions.
