A device for degassing and/or dehydrating a hydraulic oil includes a flow lance, a flow duct, and a decoupling module. The flow lance includes a restriction site via which the hydraulic oil flows under a high pressure drop. The flow duct is configured as a pipe that is located downstream of the restriction site. The quantity of oil that flows via the restriction site and a throughflow cross section of the restriction site are coordinated to one another such that a cavitation zone or supercavitation zone forms downstream of the restriction site. The flow duct has a significantly larger cross section with respect to the throughflow cross section of the restriction site. For a quiet operation of the device, the flow lance is held in the decoupling module via which the flow lance is configured to be fastened in a vibration-decoupled manner to a tank.