This work was aimed to investigate the effect of piston secondary motion on the ability of the piston rings to block the blow-by gasses. A turbodiesel engine was simulated in two conditions, with and without the secondary motion of the piston. For this purpose ©Ricardo RINGPACK simulation suite was used. According to results, the rings of a piston without the secondary motion maintain a more stable position in relation with the piston groove and with the cylinder liner, consequently they are more able to prevent more gas to flow as blow-by in the crankcase. In practical terms, for the same engine and for the same working conditions, the blow-by results to be 2 orders of magnitude lower. As the engine speed increases, the blow-by decreases for both conditions but the rings of the base piston shows instability.