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, the powdery deterioration prevention agent comprising one of an inorganic ion-exchange material and an ion-exchange resin material, and
• a housing that houses the filtering unit and the deterioration prevention unit, wherein
• out of oil fed from an oil containing unit, oil filtered by the filtering unit is fed to a part to be lubricated,
• the housing is provided with an oil inflow passage for allowing oil fed from the oil containing unit to flow into the housing, and an oil outflow passage for allowing oil filtered by the filtering unit to flow toward the part to be lubricated,
• the deterioration prevention unit includes a porous layer that retains the deterioration prevention agent and that allows oil to pass, and an intermediate layer that does not allow deterioration agent to pass and that allows oil to pass,
• the porous layer includes a first porous layer and a second porous layer that are stacked in a passing direction of oil, and
• the intermediate layer includes a plate-shaped ring between the first porous layer and the second porous layer,
• a porosity of the first porous layer on an upstream side is larger than a porosity of the second porous layer on a downstream side.