The substitution of mineral oil with vegetable oil as a lubricant in a CI engine is explored in this study. The experiments have been conducted with neat pongamia oil, blend of pongamia oil and mineral oil (50% V/V), and neat mineral oil as lubricants; and neat pongamia oil, blends of pongamia oil, and diesel in proportions of 20, 40, and 100, neat pongamia ester, and blends of pongamia ester and diesel in proportions of 20, 40, and 100 as fuel. For various combinations of fuel and lubricant, NOx, smoke, CO, HC, BSEC, EGT, and friction power were compared. It was found that there was no difficulty in operating the engine using the lubricants considered in this work. Further, it was found that the best results were recorded for the fuel-lubricant combination of neat pongamia as both fuel and lubricant