A Look At Moroso’s Air/Oil Separator

A Look At Moroso's Air/Oil Separator

Moroso is one of the most recognizable and respected suppliers of automotive parts for racing and street performance applications. The company was founded in 1968 by Dick Moroso, one of the most successful modified production drag racers on record. Dick left his racing career to start Moroso, and right off the bat began to design, test, and manufacture specialty parts for racers needs. Fast forward 50 years and Moroso is still one of the biggest names in the racing scene. With over 4,000 products and everything from engine parts to suspension and everything in between.

The Moroso Air/Oil separator is sometimes mistakenly called the catch can. A regular catch can simply traps the oil and keeps it out of the intake. However, these units are generally open to the atmosphere and cause issues like an oily engine compartment or an oil smell when the air conditioner comes on. The bigger problem is the fact that they are not EPA-compliant and usually bypass the PCV (Positive Crankcase Ventilation) system.

The far more superior Moroso Air/Oil Separator does more than just catch the oil, it also keeps harmful crankcase vapors and moisture from going back into the intake manifold, which kills engine durability and performance. The Moroso Air/Oil separator also keeps the vehicle 100-percent emissions compliant in all 50 states, so you don’t have to worry about the EPA coming down on you for anything illegal.

A properly baffled catch can will contain the residual oil and moisture, but the excess crankcase vapors are vented to the atmosphere typically by the catch can’s breather. – Thor Schroeder

“The Moroso vehicle specific Air/Oil Separators plumb inline of the PCV system and capture the excess crankcase vapors, residual oil and moisture while keeping the PCV system closed, Thor Schroeder Marketing and New Product Manager of Moroso explains. “A properly baffled catch can will contain the residual oil and moisture, but the excess crankcase vapors are vented to the atmosphere typically by the catch can’s breather. If a catch can is plumbed inline in a PCV system, then these vented crankcase vapors throw emission compliancy out the window and affect the PCV role.”

So how does the Moroso Air/Oil Separator work? Thor explains, “The Moroso Air/Oil Separators have billet aluminum bodies with heavy duty brass inlet and outlet fittings. The body is constructed of billet aluminum, with a center divider baffle that separates the “In” and “Out” ports, mesh media between the ports and the divider baffle, and mesh media under the divider wall with a perforated baffle under the divider wall and mesh media. The oil separated from the air in the media drips down into the bottom of the body of the Air/Oil Separator. This collected oil is then drained by the vehicle’s owner every 1,000 or so miles, or every race/track day that it is being used on the track. Draining the oil is accomplished by either opening up the bottom drain on Moroso large body separators or on Moroso small body separators by unscrewing the base of the body.”

Here is an excellent example of what could be hiding in your engine’s intake manifold. The Moroso Air/Oil Separator will keep the oil out of the intake allowing the engine to live longer and be more efficient.

Whether you’re building a brand new motor for your project car or have a high-mileage motor, Moroso recommends its Air/Oil Separator for both low- and high-mileage engines.

Ethanol-enriched fuels put off more moisture during the combustion process. The Moroso Air/Oil Separator is an excellent tool for collecting this extra moisture. – Thor Schroeder

“The unit is great for a new engine to start the protection, “ Schroeder explains. “Ethanol-enriched fuels put off more moisture during the combustion process. The Moroso Air/Oil Separator is an excellent tool for collecting this extra moisture. On high-mileage engines, more oil will be collected, but the separators will help the engine live longer and be more efficient.”

Some of the benefits of The Moroso Air/Oil separator include removing the oil mist before it re-enters the engine, reduction in detonation, and a decrease in deposits on the intake track, including the valves themselves. An increase in engine performance from the cleaner intake air is also typical. Not only will you have better performance, but who doesn’t want billet aluminum parts in the engine bay?

The Air/Oil separator is essential on a naturally-aspirated engine and forced induction engines alike. The separator will protect the intercooler from getting a coating of oil mist. Over time if this problem is not addressed the added build-up of oil will diminish the efficiency of the intercooler, ultimately killing power and the effectiveness of the boosted system.

We wanted to install the unit on our 2006 Chevrolet Silverado with 180,000 miles on the clock and see how it works. The idea was to drive the truck around for about 1,500 miles and examine the oil accumulation in the separator.

The Moroso Air/Oil Separator (PN 85481) included everything we needed to complete the installation, combined with comprehensive and detailed instructions with pictures. The installation process was straightforward and bolted on to a preexisting hole on the alternator bracket.


Other than a few hand tools, Moroso’s Air/Oil separator comes with everything we needed to do the install on our 2006 Chevrolet Silverado.

The first step involved taking off the Vortec intake cover and the stock PVC tube. We then assembled the billet bracket and the stainless bracket for the unit. After you get it assembled, install it on the upper hole on the alternator bracket as shown in the instructions with the supplied hardware.


The second step is to assemble the Air/Oil separator, making sure that you use Teflon tape on all of the fittings. After the fittings are secure, install the Air/Oil Separator into the billet clamp. Be sure and note the orientation of the brass fittings towards the alternator.

For step three, we needed to cut the supplied hose in half, which is approximately 30-inches in length. We then installed one piece of hose to intake and the other to the valve cover to the PVC tube. You’ll want to use the supplied zip-ties to hold both hoses together, as shown.

At this point, the installation is complete, and the entire process only took about 30 minutes. Ensure that all of the hoses are out of harm’s way and that your bolts are tight.

We drove the truck around for a few weeks before draining the separator. The truck is driven daily but is completely stock other than an aftermarket exhaust system, and so we didn’t expect to have much oil stored in the unit, if any. As we opened the valve, a little oil began to flow out, and it kept flowing into our cup, filling it up with about 4-ounces of oil! To say we were surprised would be a vast understatement. What’s crazy to think about is that this oil would have gone back into the intake manifold, though the heads, past the intake valves, on the pistons, before being pushed out the exhaust system while coating everything in its path. We will now be placing an order and installing the Moroso Air/Oil Separator on every vehicle we own, and we recommend you do the same.

These images show you how much oil was going back through our intake manifold over a few weeks. The Moroso Air/Oil Separator did an outstanding job keeping the oil out of the intake of our 5.3-liter engine.

The Moroso Air/Oil Separator is a quality piece that performs much better than your standard catch can. Not only will the engine live longer, but when you go to rebuild it, your intake manifold and heads will not be gunked up with foreign material. The units are available for the 2008-2014 Cadillac CTS-V, 2010-2015 Camaro SS, 2012-2015 Camaro ZL1, 2010-2015 Camaro SS with Edelbrock Supercharger, 2014-2019 Corvette, 2006-2013 Corvette ZO6, 1997-2004 Corvette, 1992-1996 Corvette LT1/LT4, 1999-2018 Chevy/GM Truck with LS engines, plus  universal Air/Oil Separators have been used on factory-outfitted vehicles as well as other makes and models.

For a complete listing of all of the Moroso Air/Oil Separators applications, head over to www.moroso.com to check out this product and others.

DragzineDragzine – A Look At Moroso’s Air/Oil Separator

Facebook Comments