A heat exchanger having an improved oil cooler section is provided. The oil cooler section includes a first manifold, a second manifold, an oil inlet port, an oil outlet port, cooling tubes, and a return tube. The first and second manifold are located in spaced relationship and the oil inlet and outlet port are located proximate each other toward one side of the heat exchanger. The cooling tubes are connected between the first and second manifold, each tube defining an oil flow passage. The return tube also be connected between the first and second manifold and defining an oil return passage. The oil return passage has a cross-sectional area larger than each of the oil flow passages allowing the oil to be returned along a low pressure flow path.