The present study is carried out in order to do Energy-Exergy analysis of CI engine using waste cooking oil/ rapeseed oil and biodiesel blends. Initially the biodiesel is produced from waste cooking oil and rapeseed oil using transesterification process. Thereafter the properties such as kinematic viscosity, calorific value, flash and fire point of the prepared biodiesel is done. Then performance parameters i.e., brake power, brake specific fuel consumption, brake thermal efficiency are evaluated and compared with mineral diesel. Then the Energy-Exergy analysis is carried out by writing mathematical equations and solved by using MATLAB software. It is observed from the results and discussion that, results obtained in this present work is reasonably accurate.