Abstract: A heat exchanger assembly including first and second manifolds for transferring heat between a coolant and a flow of air. Tubes extend between the manifolds for conveying the coolant therebetween. Air fins are disposed between adjacent tubes, and each air fin has a cross-section presenting a legs extending between the adjacent tubes at equal and opposing angles to one another and bases interconnecting alternate ends of the adjacent legs to present a serpentine pattern. Each base extends through an arc between the ends of the adjacent legs and defines a lead-in radius interconnecting each base with one of the legs and an exit radius interconnecting each base with the end of the adjacent leg. The equal and opposing angles are in the range of 1 to 4 degrees. The lead-in and exit radii are in the range of 0.05 to 0.15 mm. The middle radius is in the range of 0.5 to 1.5 mm.