**1. Introduction**

The technique or process of using a material to reduce friction and wear between contact surfaces, which are in relative motion, is known as lubrication. It also helps in force transmission, foreign particle transportation and heat transfer. Lubricity is the property of a lubricant to reduce the friction. Lubricants are classified into solid lubricants (e.g.: graphite), semi-solid lubricants (e.g.: grease), liquid lubricants (e.g.: mineral oils based) and gaseous lubricants (e.g.: air). Liquid lubricants are further classified into fixed oil based, mineral oil based and synthetic oil based lubricants on basis of lubricant base stock [1].

Evidences for usage of lubricants for thousands of years have been found. Several methods were adopted by human race from time to time to solve the issues regarding friction and wear. Egyptians used animal fats in ball bearings for lubrication back in 1000 B.C. Oil-impregnated lumber were used to slide building stones in the time of the pyramids and on the axles of chariots dated to 1400 BC, calcium soaps have been found [2]. Romans used thrust bearing and lubricants having rapeseed and olive oil as well as animal fat as base back in 40 A.D. Mineral oil based lubricants were widely used since 1850, but they are non-biodegradable, fast depleting and also have adverse effects on the environment [3, 4]. Nowadays, synthetic oil is considered as a better alternative to these mineral oil based lubricants.

However, these synthetic oil based lubricants are much expensive than the mineral oil based lubricants [5]. The improper after-use disposals of the available lubricants are creating severe environmental issues by polluting the water bodies [6]. Developing an efficient lubricant from a non-edible plant oil base stock is an effective solution to the above issues, as they are biodegradable, renewable and environment friendly [7]. Vegetable oil base stocks also possess high thermal stability, low volatility, good biodegradability, non-toxicity and good lubrication properties in comparison to mineral oil base stocks [8].

The present article aims at developing a lubricant from a non-edible vegetable oil. In the current work, pongamia oil (PO) is selected as the base stock due to its high oleic acid content and non-edible nature [9–14]. Formulated oil (FO) is developed by blending suitable additives in PO. Rheological, oxidative and tribological properties of PO and FO are evaluated and compared against the properties of a commercially available lubricant SAE20W40. Hence the primary objectives of the current work are to:

