Oil deterioration prevention device

An oil deterioration prevention device comprising:

• a filtering unit including a filter element that filters oil;
• a deterioration prevention unit including a powdery deterioration prevention agent that prevents deterioration of oil, wherein
• the deterioration prevention unit includes passage walls that retain the deterioration prevention agent and forms an oil passage;
• and
• a housing that axially houses the deterioration prevention unit and the filtering unit in line in an axial direction, wherein
• a horizontal sectional area of a space between an inner wall of the housing and an outer periphery of the deterioration prevention unit is smaller than a horizontal sectional area of a space between the inner wall of the housing and an outer periphery of the filtering unit, and
• the ratio of the horizontal sectional area of the space between the inner wall of the housing and the outer periphery of the deterioration prevention unit to the horizontal sectional area of the space between the inner wall of the housing and the outer periphery of the filtering unit is 0.1 to less than 1, and wherein
• the passage walls are at least one of spirally and concentrically arranged about the axis of the housing,
• the oil passage being defined between the passage walls that are adjacent each other,
• the housing is provided with an oil inflow port that is open near one end of the deterioration prevention unit in the axial direction on a side of the housing that is apart from the filtering unit, and
• the oil inflow port is open facing an end face of the oil passage in the axial direction.