The research investigates the production of methyl esters from vegetable oils, specifically karanja oil, and their application as blended fuels in diesel engines to analyze performance and emissions. The findings suggest that karanja oil methyl ester blends can be used without degrading engine performance, showing that diesel typically exhibits the highest brake thermal efficiency and lower emissions at certain blends. However, higher loads increase carbon monoxide, hydrocarbons, and smoke emissions, with the B50 blend indicating a lower smoke output, demonstrating its potential as a cleaner alternative fuel.