Abstract: In a cooling device for cooling charge air from a compressor (3) in an engine (9) and hydraulic oil from a retarder (14), a first coolant flow (m1) is provided in a coolant conduit (20). The engine (9) is cooled by the whole first coolant flow (m1). The cooling device comprises a first a first charge-air cooler (4), which is cooled by means of a second coolant flow (m2), and a second charge-air cooler (5), which is cooled by means of a low-temperature fluid (32). The cooling device further comprises a retarder cooler (17) for cooling hydraulic oil from the retarder (14), said retarder cooler (17) being cooled by means of a third coolant flow (m3). Both the second coolant flow (m2) and the third coolant flow (m3) are subflows of the first coolant flow (m1). In a method utilizing the cooling device for cooling charge air as well as hydraulic oil from a retarder (14), a second coolant flow (m2) and a third coolant flow (m3) are used, both of which are subflows of the first coolant flow (m1).