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 Moroso Air/Oil Separator for race use.  Unlike a street car system, this separator is a stand alone setup and not designed to return any gasses back to the engine. Moroso’s Air-Oil Separators plumb directly into the car’s PCV system. Using mesh filter media, they capture the majority of the engine oil that escapes the crankcase and is normally sent back to the engine through the intake.  “Removing this oil mist before it re-enters the engine reduces detonation, and deposits on the intake track, including the valves themselves,” according to Moroso’s Thor Schroeder.  

Most of the separators have a total volume of just under a quart of oil and have a drain valve to allow the collected oil to be cleanly and easily drained into another container. Moroso offers these separators in both a universal style and direct fit for multiple vehicle specific applications.

They also offer Air-Oil separators for dry sump and racing applications. These separators work much the same way that their street systems do, however they are designed for car’s running at the track rather than cars that are street driven on a regular basis. These systems do not plumb into the factory PCV system, instead they are stand alone separators.

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Moroso Air/Oil Separator for street use:  these separators capture vapor and oil that has escaped into the PCV system. They trap the liquid and send the gasses back to the engine keeping the car's emission system intact while improving engine performance.

Not long ago Moroso released a video of one of their air-oil separator systems in action. The separator was placed in-line with the PCV system on a stock Cadillac CTS-V. The car had only 24,000 miles on it, and the test drive lasted about thirty minutes. They included both hard acceleration, and just general cruising like the car would likely see in regular use. You can see several puffs of oil and water vapor enter the clear container that was substituted in place of the aluminum one for this video.  ClickMe to view it.

This is further evidence that the factory PCV system on a high-performance, unmodified engine, with low mileage is inadequate. The car’s owner states that after about a week of regular driving there’s typically about 3/4 of an inch of oil in the separator. While this may not sound like a lot, consider how much oil that is over the course of an oil change interval, a period of twelve to sixteen weeks on average.

So every twelve weeks the separator would accumulate about eight inches of oil in its reservoir. The actual volume would vary based on the dimensions of the separator, but that is definitely a substantial amount of engine oil.