An oil relief valve for lubrication systems for internal combustion engines comprising a valve body having a hollow cylindrical shape, a valve seat provided at a bottom end of the valve body, a valve plug placed in the seat, a port bored in the seat to bring the oil relief valve into fluid communication with a lubrication line which supplies oil from an oil pump to various engine parts to be lubricated, a spring mounted on top of the valve plug and adapted to urge the plug against the seat to close the port, and slits cut in the valve body and provided to bring the valve in fluid communication with an oil pan. The spring has a free length smaller than the distance of the space defined between the valve plug and the top end of the valve body.