Nowadays, increased interest among the scientific community to explore the Calophyllum inophyllum as alternative fuels for diesel engines is observed. This research is about using mixed Calophyllum inophyllum-palm oil biodiesel production and evaluation that biodiesel in a diesel engine. The Calophyllum inophyllum–palm oil methyl ester (CPME) is processed using the following procedure: (1) the crude Calophyllum inophyllum and palm oils are mixed at the same ratio of 50:50 volume %, (2) degumming, (3) acid-catalysed esterification, (4) purification, and (5) alkaline-catalysed transesterification. The results are indeed encouraging and satisfy ASTM D6751. CPME shows the high heating value (37.9 MJ/kg) but low kinematic viscosity (4.50 mm²/s) due to change a higher proportion of shorter-chain and unsaturated FAMEs, which tend to lower viscosity compared to Calophyllum inophyllum methyl ester (CIME).). The blended fuels exhibit higher brake-specific fuel consumption (BSFC) and NO_x emissions, along with lower brake thermal efficiency (BTE) and reduced CO and HC emissions compared to diesel fuel across the entire range of speeds. Among the blends, CPME5 offered better performance compared to other blends fuel ratios.