Abstract: A radiator tank is co extruded with an interior chamber, which is subdivided into at least two subchambers by at least one integral dividing web. The web is recessed from one end cap of the tank by a clearance space, but brazed to the other end cap of the tank. An oil inlet opens into one subchamber, remote from the clearance space, and an oil outlet opens into the other subchamber, also remote from the clearance space. Radiator coolant is conventionally fed into the remainder of the tank, sealed from the subchambers, but thermally exposed thereto across a common inner wall. Oil fed into one of the subchambers is forced to follow an efficient, serpentine path that is an integer multiple of the total end to end length of the basic tank, enhancing conduction.