A heat exchanger for cooling oil, including a plurality of pan-shaped heat-transfer plates stacked onto one another to define alternating channels for coolant and oil, a mounting plate soldered on one side to a side of the stacked plates and adapted to mount on its opposite side to a separate component. Openings through the heat-transfer plates and the mounting plate are provided for the passage of the oil and of the coolant, where the openings in the mounting plate have recesses therearound on the side opposite the heat-transfer plates. The recesses are adapted to receive seals therein.