The main focus of this research is to examine the changes in engine performance, combustion and emissions caused by using ethanol of plastic oil (EPO) as biodiesel. Experiments with the engine load, injection pressure (IP), fuel mixture and supercharging (SC) pressure in a different compression ratio (CR) engine are carried out. Brake thermal efficiency indicated mean effective pressure, specific fuel consumption, combustion pressure, ignition delay, heat release rate, hydrocarbon, carbon monoxide and nitrogen oxides emission and many more are among the variables for which Response Surface Method (RSM) prediction models are developed using the experimental data. The optimality test is performed so that optimal engine performance and emissions can be achieved. Keeping the CR fixed at 25 and varying the SC conditions at 75 load, experiments are conducted with fuel blends of 25, 50 and 75 biodiesel with pure diesel. The results of the tests suggest that the supercharged engine is superior to the diesel engine in terms of output and emission levels. Blends of biodiesel and conventional diesel burn similarly. © 2025 Elsevier B.V., All rights reserved.