Installing Moroso’s Air/Oil Separator On Project Silver Bullet

The PCV system on any vehicle is designed to capture and recirculate gasses that buildup in the crankcase as part of the combustion process. This system is also supposed to prevent oil from being moved into the induction system during that process via the PCV valve. However, when forced induction is added to an engine crankcase pressure increases, thus the chances of oil getting past the PCV system and into the intake increase dramatically.

Our Project Silver Bullet 2013 Mustang is sporting a ROUSH Performance Stage 2 supercharger for street and strip high performance. To stop unwanted oil and other vapors from entering the intake via the PCV system we’re installing one of Moroso’s Air/Oil separators, part number 85485 that is designed specifically for this application.

Included with Moroso’s Air/Oil separator is everything needed for installation including hoses, fittings, and the mounting brackets.

Why Separate The Oil And Air

Under high temperatures and crankcase pressure engine oil can vaporize and be drawn into the PCV system, escaping past the PCV valve and then getting circulated back into the incoming air an fuel charge from the intake manifold. This problem is made worse by the high temperatures associated with forced induction applications causing more oil to be vaporized.

When mixed with the incoming air/fuel charge this oil vapor alters the effective octane level of the fuel being burned since its flashpoint is higher than that of gasoline. It can also coat the intake manifold runners, valves, and tops of pistons or leave behind despots. This oil coating can catch other small particulate matter in the incoming stream as well.

The billet filter media inside the separator traps oil in the PCV system while still allowing the crankcase gasses to pass back into the intake to be burned.

Moroso’s Air/Oil separator uses a special billet filter media to trap the oil vapors as they pass through the PCV system. This media allows gasses to continue traveling through the PCV system but traps the liquid or vaporized oil mist in the separator. The separator can then be emptied at periodic intervals and the oil returned to the crankcase or disposed of properly.

Top Row: Left: We mounted the Air/Oil separator bracket to the passenger side strut tower. Center: We disconnected the PCV hoses from the passenger side of the supercharger and valve cover. Right: We then replaced the factory quick connect where it plugs into the supercharger with the new 90-degree fitting supplied by Moroso. Bottom Row: Left: We connected the hose that will runs from the 90-degree fitting we installed to the Air/Oil separator. We then connected the outlet side line from the separator to the PCV inlet on the supercharger. Center: We installed the supplied brass 90-degree fittings into the Air/Oil separator for the inlet and outlet. Right: We then installed the air oil separator into the mounting bracket and tightened it down. With the hoses connected installation is now complete.


While the Moroso Air/Oil separator sounds like a complex piece of hardware, it’s actually a simple bolt-on installation that anyone with average mechanical skill should be able to install on their Mustang or other high performance car in an hour or less. Moroso includes the necessary hardware, fittings and additional PCV hoses, as well as a mounting bracket for installing the separator into the existing PCV system. There’s no fabrication required. If you can use basic hand tools you’re competent enough to do this install.

Our finished installation looks almost factory, allows for easy access to empty our separator and will ensure that oil from the PCV system stays out of our intake.

We’ve outlined the installation of the air/oil separator in the photos and captions that we included with this story. With our install completed we can head back out on the track and the streets confident that oil is not entering the combustion chamber when we stomp the loud pedal.

Article Sources

About the author

Don Creason

Don Creason is an automotive journalist with passions that lie from everything classic, all the way to modern muscle. Experienced tech writer, and all around car aficionado, Don's love for both cars and writing makes him the perfect addition to the Power Automedia team of experts.
Read My Articles

Blue Oval Muscle in your inbox.

Build your own custom newsletter with the content you love from FordMuscle, directly to your inbox, absolutely FREE!

Free WordPress Themes