In the present work the evaluation of coconut and palm oil as lubricants in four-stroke engine was carried out and the performance was compared with commercially available engine oil. The tribological properties of oil samples collected from the engine at regular interval were evaluated by means of four ball tester. The emissions from engine were monitored by using exhaust gas analyzer. It was observed that antiwear properties of fresh vegetable base oils and engine oil were comparable at ambient conditions. The observed deviation with usage was linked to the oxidation and the absence of additives in vegetable oil. The increased wear with commercial engine oil was due to depletion of additives. Increased fuel efficiency and reduction in the concentration of oxides of carbon and nitrogen in the emission observed with vegetable oil based lubricant was linked to its high flash point.