Recycling plastics into energy sources is the most promising method for cutting down on pollution and trash. In this regard, predictions of adiabatic engines using pistons with thermal barrier coatings (TBCs) were made to reduce in-cylinder heat rejection, safeguard the underlying metallic surfaces from thermal cracking, and indeed reduce engine emissions. This study compares the predicted thermal and physical parameters of Plastic Waste Oil (WP) with its diesel blends in fixed proportions of WP10D90 (10% plastic oil, 90% diesel), WP20D80, WP30D70, WP40D60, and WP50D50 to diesel values. The study further explores the concept of the utility function to evaluate the best-ranked fuel blend in each category of various performance characteristics namely BTE, BSFC, UHC, CO, and NOx. Additionally, the effect of the thermal barrier piston coating on CI engine performance metrics and emissions was studied and compared to those achieved with regular diesel oil. When compared to diesel, the results state that the WP40D60 blend has the highest brake thermal efficiency, i.e., 31.62% at 80% load, and the lowest NOx emissions at all load conditions. In addition, it was further observed that the WP20D80 has lower hydrocarbon (HC) emissions at 20% load and an increment in CO emissions for all blends and load combinations. Overall, WP30D70 has come up with the best fuel as per the Utility function.