<p>An oil filter comprising a housing opened at one end, a first separator unit in the housing for removing solid contaminants from the oil and a second separator unit for removing gaseous contaminants. The first separator unit includes a cylindrical filter element and upper and lower end plates attached to the upper and lower ends of the filter element. The second separator unit is disposed in the space defined by the inner periphery of the filter element and between the upper and lower end plates. It includes a chamber arranged to generate a vortical flow of the oil introduced thereof to thereby separate gas-rich oil which gathers in an axially central portion of the chamber, a first outlet for discharging the gas-rich oil and a second outlet for the oil containing little gaseous contaminants, the first and second outlets extending into the housing from the open end thereof.</p>