Abstract: The invention concerns a heat exchanger (1) comprising an inlet tank (2), having a fluid inlet (4),and an outlet tank (3), having a fluid outlet (5),and a core (6) of tubes (7, 8) joining said inlet tank (2) and said outlet tank (3) together and creating a plurality of fluid flow paths (P1) from said inlet tank (2) to said outlet tank (3), wherein said tubes (7, 8) belong to a primary and a secondary group of tubes(7, 8). According to the invention said inlet tank (2) and said outlet tank (3) have header plates(9, 10), which form core interfaces and comprise throughout identical tube insertion orifices for both the primary group of tubes (7) and the secondary group of tubes (8).Further, the tubes being a member of the primary group are base tubes (7)and the tubes being a member of the secondary group are adaptation tubes (8), which differ from the base tubes (7) and a reused to locally change properties of the heat exchanger (1) in critical areas of the heat exchanger (1).