Blends of algae oil with diesel can act as a substitute for diesel are expected to provide organized efficiency and better emission characteristics by controlling the parameters of the compression ignition engine. The addition of antioxidants like pyrogallol and butylated hydroxy toluene can make biodiesel more effective. An Analytical Hierarchy Process and the Taguchi-Grey method are combined for the first time in the compression ignition engine process to optimize the parameters for better performance and reduce toxic emissions. For analytical hierarchy process analysis, an expert’s opinion is collected for the response variables to assign the weightage to the variables. For better performance and reduced emissions, the optimum process parameters are found to be injection timing at 23°, pyrogallol at 0 ppm, and butylated hydroxy toluene at 500 PPM. Furthermore, a confirmation test was conducted to confirm the obtained results from the optimization process, and the results showed that the brake thermal efficiency is enhanced by 3.6 % and NOx is reduced by 6 %. However, the smoke from the CI engine is increased by 10.4 %.