Abstract: An apparatus and method are provided for maintaining a substantially constant partial vacuum in the crankcase of an internal combustion engine. Maintaining the partial vacuum, in addition to essentially eliminating crankcase emissions, substantially reduced tailpipe emissions of carbon monoxide and unburned hydrocarbons as evidenced by a test conducted according to California Air Research Board test method 505 (hot). The crankcase partial vacuum also has the added benefit of reducing the rate at which the engine lubricating oil was contaminated.