An oil degradation suppressor according to one aspect of the present invention contains a reactant having an ability to adsorb a given component in an oil such as an acidic anion, and a gel-like material to hold the reactant. The reactant is preferably a hydrotalcite-like compound. The gel-like material contains a highly heat resistive gel and an amphiphilic solvent. A gel-like member containing the reactant and the gel-like material is disposed in a casing, and thereby an oil filter is provided. The gel-like material can work for supporting the reactant suitably.
