The latest developments in the engine’s design aim to maximize the power output, downsize the engine, and minimize the fuel consumption. This paper investigates the thermomechanical loads on the piston of a turbocharged diesel engine. The main emphasis is the effect of increasing the boosting pressure on the piston loading until the possible maximum engine power is achieved. Also, it proposes the modification of the piston design in order to increase the durability for more power loading and decrease the total mass. The temperature distribution on the piston body, the corresponding thermomechanical deformations, the stress distribution, and the safety factor is excessively calculated. Finite element methods (ANSYS workbench) is used to analyze the thermomechanical loads applied to a three-dimensional model. The study is applied to the piston of a 300 hp diesel engine (base case) in order to increase the engine power by 17% (upgraded one). The piston remains within safe conditions and can withstand further loads until the extra power increase reaches 56%. In order to withstand more loads with low fuel consumption, the piston under consideration may be modified in several methods. First, opening an oil-cooling channel inside the piston crown. Second, decreasing the thickness and length of the piston skirt and pin bosses. Finally, increasing the diameter of the piston pinhole and the fillet radius around pin bosses. Analytical investigations show that these modifications would reduce the maximum temperature and deformation at the piston crown by 32.4% and 31.4%, respectively, with no increase in the stresses. The modified piston can withstand, safely, the thermomechanical loads when the engine power increases up to 90% with a lower mass by 15.8%.