What does an oil catch can do?

Signs and symptoms of an oil catch can failure

An oil catch can is an accessory that captures and filters excess oil from entering the engine’s intake manifold. It’s not always fitted by manufacturers in vehicles, but they are commonly found in diesel, turbocharged and supercharged engines.

Want the best performance out of your vehicle? Natrad has a range of high-quality oil catch cans for turbo diesel engines aimed to optimise performance, reduce emissions, and protect components from blow-by. We can also help your vehicle remain compliant with national emissions standards.

To view our range of oil catch cans and related products, ask a qualified technician at your nearest Natrad store today.


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What does an oil catch can do?

oil catch can

An OCC (oil catch can) has multiple purposes. Here are some of the most common:

  • Oil catch cans are often fitted as an aftermarket accessory to optimise engine performance
  • They help reduce emissions to ensure a vehicle complies with regulations
  • They help protect engine parts from contaminants

Also known as oil/air separators, OCCs capture oil droplets or mist from the circulating air in the engine breather and the engine’s intake system.

Depending on the vehicle, this oil/air mixture also circulates through an EGR system (exhaust gas recirculation) and is then sent back into the engine intake. The problem with this is the potential for clogging over time as excess amounts of oil build up on the inlet. This leads to ineffective performance and increased emissions since exhaust gasses can’t be recirculated effectively.

An oil catch can is used to filter and catch the excess oil before recirculation. Its other goal is to prevent oil mist or vapour from reaching the positive crankcase ventilation valves, known as blow-by. Blow-by is the loss of compression as it leaks past the piston rings into the positive crankcase ventilation valve, causing positive crankcase pressure. Once the oil droplets have been caught, clean air can be passed back into the engine intake for an optimised combustion chamber.

In which applications are oil catch cans most commonly found?

Catch cans can be retrofitted into many vehicles but are common in diesel and turbo-charged port-injected engines due to their increased emissions output. Using an oil catch can is known toextend the lifespan of components in the EGR system and the engine.

Some (usually older) cars were designed with crankcase breathers that vented the exhaust gas mixture directly into the atmosphere. As emissions restrictions come into place and laws become more strict, this is no longer possible. Hence the need for EGR systems and the oil catch can.

Where does an oil catch can go?

An oil catch can is often an addition to an existing engine and can be fitted into tight space restrictions. Some vehicles place it between the positive crankshaft ventilation valve (PCV) and the air intake port system. A hose is connected to the catch can where the air/oil mixture is directed through it. The dirty air passes through the filter, and once all the oil is collected, it exits as clean air back into the intake. (This may vary depending on the vehicle).

oil catch can diagram

Image Credit: Ben Potter from All Car And Truck

Signs and symptoms of catch can failure

It may not be immediately obvious that the catch can has failed, as it likely won’t create any immediate symptoms. However, over time it may lead to EGR clogging, increased emissions, reduced performance, and misfiring. This is detrimental to the overall performance of your vehicle, and can make it non–compliant with local emissions standards.

To avoid this, you can use preventative maintenance to keep it in good working condition. This means having the excess oil cleared from the can regularly (at usual service intervals) to avoid build-up. In the case that your catch can has failed, Nip into your nearest Natrad store and talk to a specialist. They can advise the best solution for you and provide a detailed quote.

What next

Natrad’s network of national workshops offers servicing, repairs, and inspections for a variety of automotive systems. If you want to know more about catch cans and the best solution for you, simply find your nearest workshop and drop in! Our team of experts can help your vehicle operate at peak performance while ensuring that it remains compliant with regulations.

Natrad has a range of high-quality oil catch cans for diesel and forced-induction engines, just find your nearest store today.


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