Insulation of pistons in engines is aimed at reducing the heat losses and thus increasing the indicated efficiency. Thermal barrier coatings (TBCs) were used to simulate adiabatic engines with the intention not only for reduced in-cylinder heat rejection and thermal fatigue protection of underlying metallic surfaces, but also for possible reduction of engine emissions. The application of TBCs reduces the heat transfer to the engine cooling jacket through the combustion chamber surfaces (which include the cylinder head, liner, and piston crown) and piston rings. The insulation of the combustion chamber with this coating, which is ceramic based, influences the combustion process and hence the performance and exhaust emissions characteristics of the engines. In the scenario of fast rising oil prices, insulation technologies are gaining importance as they help in saving fuel. A plasma sprayed thermal barrier coating was deposited on top of a piston for a Diesel engine and its effect on the engine performance is studied. It is found to increase thermal and mechanical efficiency.