A diesel engine with variable compression was used to test the engine performance and emission characteristics of diesel, biodiesel, and biogas fuels together. Grey relational analysis was used to solve the issue so that the best process response could be found with a minimal number of trial runs. It was expected that a particular set of input parameters would produce the optimal response characteristics when used as performance indices along with the grey relational grade and. It has been established that a diesel engine can operate well with 70% of the mixture without significantly changing its emissions or performance.