A rotating machine comprising such as an axial power turbine or a turbocharger has a housing with a bearing cavity and a chamber separated by a first wall. A shaft is rotatable about an axis in the bearing cavity, extends through an opening in the first wall and is mounted for rotation on a bearing assembly provided in the bearing cavity. An oil sealing arrangement including an oil diffuser device is arranged on the shaft for displacing oil away from the shaft as it rotates. This restricts the flow of oil to the opening. The oil diffuser device defines a diffuser passage between the bearing assembly and the first wall, the passage extending outwardly of the axis.