The need for sustainable alternative fuels is becoming increasingly urgent because to the rapidly expanding demand for automobiles and the growing concerns over the fossil fuel diminution. This research looks into how biodiesel, specifically blends made from rapeseed oil (RSO), can fill this new need. The RSO is created through transesterification, which yields a biodiesel with characteristics that meet ASTM requirements. In a 5.1 kW, single-cylinder, turbocharged Diesel engine (Turbo-DE), the performance, emissions, and combustion (P-E-C) characteristics of several RSO-diesel blends (B20, B40, B60, and B80) are examined and contrasted with those of pure diesel. According to the findings, brake thermal efficiency slightly decreases as biodiesel proportion in the blend rises. The environmental advantages of these blends are offset by a sizable decrease in smoke, CO, and hydrocarbon emissions. On the other hand, greater biodiesel ratios result in higher emissions of NOx and CO2. The thermal efficiencies of the brakes for diesel, B20, B40, B60, and B80 blends were found to be 29.3%, 28.6%, 27.9%, 27.2%, and 26.9%, respectively, in the detailed results. While smoke emissions decreased from 55% (diesel) to 40% (B80), NOx emissions ranged from 1556 ppm (diesel) to 1718 ppm (B80). The B20 blend’s combustion characteristics closely resemble those of diesel, with maximum cylinder pressures and ignition delay of 78 bar, 73 bar, 20%, and 18%, respectively, for diesel and B20. These results offer a good starting point for additional investigation into sustainable alternative fuels by shedding light on the prospective performance and ecological impact of biodiesel-diesel mixes.