The study aims to investigate the real-time engine performance in terms of brake power, thermal efficiency and emission characteristics of a diesel engine. Waste vegetable oil samples were collected from several sources, mixed, and refined before transesterification. Test fuels include ultralow sulfur diesel and seven waste cooking oil biodiesel blends. Real-time data acquisition of engine performance was implemented using labview program while following the society of automotive engineers (SAE) power test code. Results showed that acid number was reduced by 99% after refining. NOx has reduced by 33% while thermal efficiency increased by 7.5% when using waste vegetable oil biodiesel.