A new forged steel piston has been designed that shows advantages for use in highly loaded diesel engines in two possible applications: 1The reliability of a forged steel piston for peak cylinder pressures up to c.18 MPa with a weight reduced to near that of an aluminum piston, if the pin is taken into consideration. 2A piston with higher loadability than an articulated piston with advantages in weight at a competitive price. Design criteria are presented as well as results from a three dimensional Finite Element Analysis. The production process is described. Results from engine development tests are shown, applying this new piston in a heavy-duty truck engine.