Disclosed herein is a breather assembly for use in an internal combustion engine and a method of operating an internal combustion engine. In at least one embodiment, the breather assembly includes an input chamber for receiving blow-by gas, the input chamber bounded at least partially by a crankcase exterior, and a standpipe situated inside the input chamber for directing blow-by gas into the input chamber. Additionally, the breather assembly can include an input drainback passage situated inside the input chamber and an output chamber situated adjacent the input chamber, the chamber having an inner wall with a one-way valve that allows blow-by gas to flow from the input chamber to the output chamber. The breather assembly can also include an output drainback aperture situated in the inner wall and an output chamber housing that substantially encloses the output chamber and includes an exhaust port for exhausting blow-by gas.