This study evaluates the production, blending, and engine performance of biodiesel derived from Argemonemexicana seed oil as a sustainable alternative to conventional diesel. Crude oil was extracted from seeds collected across different regions of India and converted into biodiesel via a two-step transesterification process, comprising acid-catalyzed esterification followed by base-catalyzed transesterification to reduce free fatty acids and optimize fatty acid methyl ester yield. The synthesized biodiesel was blended with commercial diesel at varying concentrations and characterized for fuel properties. Engine performance and emission tests were conducted on a single-cylinder, four-stroke diesel engine, assessing parameters including brake thermal efficiency, specific fuel consumption, and exhaust emissions (NO, HC, CO, CO?, and O?). Among the tested blends, B10 (10% biodiesel) exhibited the most favorable performance, achieving stable engine operation, lower fuel consumption, and an improved emission profile compared to neat diesel and higher biodiesel blends. Higher biodiesel content, such as B15 (15% biodiesel), resulted in slightly reduced engine stability and increased fuel consumption due to its lower calorific value and higher viscosity. These results demonstrate that A. mexicana biodiesel, particularly at 10% blending, offers an optimal balance between engine efficiency, fuel economy, and emission reduction, confirming its potential as a renewable diesel substitute.