Abstract: A unit (1) for accumulating and degassing oil in an oil system comprising a reservoir (2) provided with a first chamber (3) in which the oil is subjected to atmospheric pressure and in which the oil volume is allowed to vary, a second chamber (4) which is intended to be at least nearly completely filled with oil and in which the oil is kept separated from direct contact with surrounding air, and a flow passage (7) between the chambers. A air-tight flexible member (11) is arranged in the first oil accumulation chamber in order to keep the oil therein separated from direct contact with surrounding air. The unit also comprises an apparatus (20) for degassing oil, which is connected to the reservoir and comprises an entrance (21a) for feeding oil into the apparatus (20), an exit (22a) for oil connected to the reservoir, and a degassing room.