A catch can collects oil vapors that your engine normally recycles back into the combustion chamber

A catch can is a small tank that sits between your engine's crankcase ventilation system and the intake manifold. As your engine runs, it produces blow-by — unburned fuel and oil vapor that escapes past the piston rings. Instead of letting those vapors go straight back into the intake, a catch can intercepts them, separates the oil from the air, and stores the oil in a reservoir you empty by hand.

Motion Raceworks makes catch cans designed for street cars and track vehicles. Their cans use baffles and sometimes a filter element to trap oil droplets while allowing air to flow back into the engine. The result is less oil contamination in your intake valves and fuel system, which some owners report leads to cleaner combustion and easier cold starts.

Whether a catch can is worth installing depends on your engine type, driving style, and how much you value the maintenance routine of emptying it regularly. It is not a modification that fixes a broken engine — it is a preventive tool that reduces one specific wear mechanism.

Key Takeaways

  • A catch can traps oil vapor before it enters the intake, reducing carbon buildup on intake valves over time.
  • Motion Raceworks catch cans are available in different sizes and configurations depending on your engine bay space and flow requirements.
  • Installation requires routing hoses from the crankcase vent line to the catch can inlet and then back to the intake or atmosphere.
  • You must drain the collected oil from the reservoir every few hundred miles to a few thousand miles, depending on engine condition and driving intensity.
  • A catch can does not increase horsepower or fix engine problems; it is a maintenance aid that may extend the life of intake components.

How blow-by gets into your intake system

Every piston has a small gap between it and the cylinder wall. As combustion happens, some of that pressure and unburned fuel slip past the rings — this is blow-by. Your engine has a crankcase ventilation system (PCV system on older cars, or a closed loop on newer ones) that routes this vapor somewhere so pressure does not build up inside the block and blow out seals.

On most modern engines, that vapor goes straight back into the intake manifold or the intake tract. The problem is that this vapor carries oil droplets. Over thousands of miles, those droplets stick to intake valves, fuel injectors, and intake ports, forming a carbon layer that restricts airflow and makes the engine work harder to breathe.

A catch can intercepts the vapor before it reaches the intake. The baffles inside slow the flow and let gravity pull oil droplets down into the reservoir, while the cleaned air continues on. This is especially useful on turbocharged engines, which tend to produce more blow-by, and on direct-injection engines, where intake valve deposits are harder to clean once they form.

What Motion Raceworks catch cans include

Motion Raceworks offers several catch can models, each designed for different engine sizes and installation locations. Their cans typically come with a reservoir (usually aluminum or plastic), internal baffles, a drain plug at the bottom, and a vent line that can be routed to atmosphere or back to the intake.

Most kits include the hoses and fittings needed to connect the can to your engine's crankcase vent line. Some models have a spin-on filter element that you replace periodically, while others rely on baffle separation alone. The size you choose depends on your engine's displacement and how much blow-by it produces — a larger engine or a heavily modified one may need a larger reservoir to avoid overfilling between drains.

Installation location varies by vehicle. Some owners mount the can in the engine bay, others under the car or in the trunk, depending on space and hose routing. Motion Raceworks publishes fitment guides for popular platforms, though custom routing may be necessary on less common vehicles.

Installation basics and what to expect

Installing a catch can is a straightforward plumbing job that most owners with basic tools can handle. You locate your engine's crankcase vent outlet — usually a hose coming from the valve cover or the block — and disconnect it from the intake. You then run a hose from that outlet into the catch can inlet, and run another hose from the catch can outlet back to the intake or to open air, depending on your setup.

The catch can itself mounts to the frame, engine bay, or chassis using brackets. You find it so it does not vibrate loose and position it so the drain plug is accessible. Some owners route the vent line to atmosphere (venting to the outside air) rather than back to the intake; this is simpler plumbing but may increase emissions slightly and is not street-legal in some regions.

Once installed, the system works passively — no electronics or moving parts. The only maintenance is draining the oil that collects in the reservoir. How often you drain depends on your engine's condition and driving style. A stock engine might need draining every 2,000 to 5,000 miles, while a heavily modified or turbocharged engine might need it every 500 to 1,000 miles.

Draining and maintaining your catch can

The drain plug sits at the lowest point of the reservoir. You unscrew it and let the collected oil drain into a container — the same way you would drain an oil pan. The oil that comes out is a mixture of unburned fuel, water vapor, and engine oil, so it should be disposed of properly, not poured down a drain.

Some owners check the catch can every time they fill the gas tank, while others set a reminder based on mileage. If you forget to drain it and it overfills, excess oil can be sucked back into the intake, which defeats the purpose. A few catch cans include a sight glass so you can see the oil level without opening the reservoir.

If your catch can has a replaceable filter element, you swap it out according to the manufacturer's schedule — usually every 10,000 to 20,000 miles, though this varies. A clogged filter reduces airflow and can create backpressure in the crankcase, which is why staying on top of maintenance matters.

When a catch can makes the most difference

A catch can is most useful on turbocharged engines, which produce more blow-by due to higher combustion pressures. It is also valuable on direct-injection engines, where intake valve deposits are harder to remove once they form — the catch can prevents them from building up in the first place.

On a stock naturally aspirated engine with a healthy PCV system, the benefit is smaller but still real. You may notice easier cold starts, slightly smoother idle, or a cleaner engine bay over time. On a modified engine running high boost or high RPM, the benefit is more obvious — you are preventing a real maintenance problem rather than solving a theoretical one.

Track cars and high-mileage street cars see the biggest payoff because they spend more time at high load, producing more blow-by. A weekend warrior or daily driver with moderate mileage will see slower accumulation of deposits, so the urgency is lower.

Catch cans versus other intake cleaning methods

A catch can is preventive — it stops deposits from forming. Other methods, like fuel system cleaners or intake valve cleaning services, are reactive — they remove deposits after they have built up. The two approaches work together: a catch can reduces how fast deposits form, while a cleaner removes what does accumulate.

Some owners use both. They install a catch can to slow deposit formation, then run a fuel system cleaner or have the intake valves professionally cleaned every 50,000 to 100,000 miles. This is more expensive than either method alone but is common on high-performance or turbocharged cars where intake cleanliness directly affects power output.

On older carbureted or naturally aspirated engines, a catch can is less critical because the PCV system design is simpler and deposits form more slowly. On modern direct-injection engines, especially turbocharged ones, a catch can is increasingly seen as standard maintenance rather than an optional upgrade.

Frequently Asked Questions

Will a catch can increase my horsepower?

Not directly. A catch can does not add power by itself. However, by keeping intake valves cleaner, it may help your engine maintain its original power output longer, and on some direct-injection engines, removing carbon buildup can restore a small amount of power that was lost to deposits. The benefit is measured in preventing loss, not in adding new power.

Can I vent the catch can to atmosphere instead of back to the intake?

Yes, and it is simpler to install. However, venting to atmosphere means you are releasing unburned fuel vapor and oil mist into the air, which increases emissions. Many regions restrict or ban this setup for street cars. Check your local emissions rules before choosing this route. Most street cars route back to the intake to stay legal.

How do I know if my catch can is working?

The oil that collects in the reservoir is your proof. If you drain it and find a significant amount of oil and fuel residue, the can is doing its job. If the reservoir stays nearly empty, either your engine produces very little blow-by, or the hoses are not routed correctly. A sight glass makes this check easier.

Do I need a catch can if my engine is stock?

Not necessarily. A stock engine with a functioning PCV system will run fine without one. A catch can is most useful if you drive aggressively, have high mileage, or own a turbocharged or direct-injection engine. If you are concerned about intake cleanliness, a catch can is cheaper insurance than a professional intake cleaning service down the road.

What happens if I do not drain the catch can?

If the reservoir overfills, excess oil gets sucked back into the intake, which defeats the purpose and can actually increase carbon buildup. You may also see oil vapor escape from the vent line. Regular draining — every few hundred to few thousand miles depending on your engine — keeps the system working as intended.