The present work focuses on the energy, exergy, and economic study of a compression ignition engine working with waste plastic oil (WPO). Blends like 10% to 30% by volume of WPO with diesel are prepared and investigated experimentally to evaluate the performance parameters. The thermal efficiency and exergetic efficiency are found to be increased by 3.38% and 6.92% with an increase in WPO blend up to 20% compared to the neat diesel case. The cost rate of inlet fuel for WPO20 is found to be decreased substantially from that of diesel. Moreover, the sustainability index (SI) of WPO20 by 1.38% higher than diesel ensured the extended durability of the engine and lesser damage to ecological factors.