Air Oil Separator vs. Catch-Can – Which One Is Better?

An air-oil separator and catch-can are part of the PCV system of every vehicle. They may come pre-installed, or you have to install them while modifying your automobile. Both are oil filters, and establishing an oil filter on your vehicle will improve your engine performance compared to other cars. These both do almost similar jobs but are designed differently. To clarify the confusion, we have described the air-oil separator vs. catch-can and which one is better.

Our Pick

We picked the catch-can as our winning because of its advantages over an air oil separator in the first place. An oil catch-can makes more sense if you use a small quantity of oil between the duration of oil changes. It is less expensive than an air oil separator and works perfectly for routine car use. It has a simple design, effectively captures the oil droplets, and lets the gases go to the inlet when appropriately installed. The catch-cans are helpful to prevent carbon buildup in the air intake port and intake valves.

Air Oil Separator

An air-oil separator(AOS) is valuable equipment. It separates the oil in the engine from the compressed air. It is an oil catch-can designed to have more baffles than simple catch-cans. The basic idea behind developing an air-oil separator is to separate air from oil. This means that the air must be pulled from the machine while oil must be kept inside the vehicle’s engine for lubrication.

Air Oil Separator

After separation, it sends the oil back to the engine, and you don’t have to drain the AOS systems manually. It returns the separated oil vapors to the engine, avoiding them from going into the air intake. Besides, an air oil separator helps you find less carbon buildup in air intake valves and use oil vapors as fuel instead of just throwing them into the atmosphere.

Air oil separators are the best idea when planning to go on a race track with your vehicle. They increase the car’s performance because they prevent the fuel mixture go directly into the air intake.

  • Its baffles help return the captured oil to the engine
  • Catches the oil from blow-by air efficiently
  • Need low maintenance as you don’t have to remove the captured oil after some time manually
  • Increases the engine performance by avoiding the oil passage to the air intake
  • Have the capacity to capture large volumes of oil vapors
  • Works best to go on a race track or long tours with your vehicle
  • Expensive as compared to oil catch-cans

Oil Catch-Cans

The basic idea of oil catch-cans is to separate oil from the fuel mixture the same as the air separator, but with a different design and efficiency. A catch-can is installed in the engines with the existing PCV system that releases the crankcase pressure. PCV is an abbreviation of positive crankcase ventilation. This system helps the vehicle vent the air and mist oil through the crankcase en route towards the engine and then back to the engine’s air intake.

Oil Catch-Cans

Some of the oil will be deposited in the air intake during this process, and this deposited oil needs to be cleaned to avoid carbon buildup. For this purpose, some engines need to install an air oil separator or a catch-can. An engine’s intake system is highly sensitive and will lose functionality after carbon buildup if the oil leaks to the intake manifold.

A catch-can prevents the oil from the PCV system as it is directly connected to the intake system. When air passes through the crankcase, it reaches an oil catch-can. The oil catch-can has baffles. These baffles trap all the oil inside and prevent them from going to the intake valves. The only thing you have to take care of is the usage of a catch-can that has double capacity or volume compared to the expected oil filling so that it doesn’t fill to itself. If it gets filled, it can cause leakage. You have to drain it before the catch-cans fill.

  • Separates all the oil from the blow-by air of the PCV system
  • Work best for routine car usage
  • Oil catch-can costs less than an air-oil separator
  • Collects the oil residue from the air-oil mist and prevents its return to the engine
  • Most oil catch-cans usually come with double capacity compared to oil filling
  • You have to drain the oil manually after some time
  • Complex maintenance

Similarities Between the Air-Oil Separator and Oil Catch-Can

  • Air oil separators are similar to oil catch-can because they separate oil vapors to prevent oil from entering the intake manifold.
  • Both devices work on the same principle.
  • You install both of them along with a crankcase.
  • They have baffles that are specifically designed to catch oil.
  • They both work to increase the performance of an engine.
  • You have to take care of both air oil separators and catch cans as their maintenance is essential for engine performance.

Differences Between the Air-Oil Separator and Oil Catch-Can

If we think about the oil separator vs. catch-can, the main difference between the air-oil separator and catch-can is their design. The air-oil separator has a design to separate the blow-by air from the oil vapors and return these oil vapors to the engine to use as fuel.

Air Oil Separator vs. Catch-Can

The oil catch-can has a different structure, and it does not send the oil vapors back to the engine; instead, you have to remove this oil from the can manually after some time. The other significant difference is the number of baffles. An air-oil separator has comparatively more baffles than an oil catch because it has to return the captured oil to the engine.

A catch-can reduce blow-by air and the oil passage to the air intake because the accumulation of oil in the atmosphere can result in carbon buildup, affecting the vehicle’s performance.

Frequently Asked Questions

1. Why should we use an air-oil separator or an oil catch-can?

It is necessary to use an oil catch-can or air-oil separator because the oil vapor can create carbon deposition. In the worst case, they can also lower the effective octane of the fuel, which can result in tuning issues or knock, etc.

Nowadays, almost every car engine has installed the PCV system, and they increase-performance of a vehicle. While the engine is running, the piston rings allow some air to pass through the cylinder to the piston and eventually reach the engine’s crankcase.

When the air mixes with the oil vapors, it is called blow-by. The vehicle needs to vent this blow-by air and oil mist from the crankcase either with the help of an air oil separator or an oil catch-can. Otherwise, it will blow the gaskets of valve covers of the intake, damage the engine and decrease the performance of the motor.

2. Is it necessary to use an oil filter with the direct injection engines?

An oil filter is an essential addition to the direct injection engine to make it work longer. Air oil separators or catch-can are necessary because a direct injection engine mixes fuel in the air intake. It cannot automatically clear the PCV system or air intake, so an oil filter can help here.

If you do not use an oil filter, it can cause carbon buildup at the back of the air intake port or intake valves of the direct injection engines. Air oil separator and catch-can are also crucial for a motor having a turbocharged engine.


A separator or catch-can is beneficial for a turbocharged or direct-injection engine. Besides the main differences, they both work on the same principle of oil separation. You can use an oil catch-can for routine life usage of a vehicle, but if you want to go on a long track, you should install oil separators. This article aims to help you make an informed decision regarding air-oil separator vs. catch-can. We hope now you can decide what suits your system best.

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