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A good quality oil catch can and modern common-rail turbo-diesel engines are a match made in heaven. While there are many opinions out there on the internet, from what I have seen with my own eyes, I’m convinced that a (I’ll say it again – good quality) catch can kit is well worth the asking price.
They are relatively cheap, and in kit form are easy to install for the home DIYer. Most importantly, they provide peace of mind that harmful carbon-filled sludge isn’t filling your vehicle’s vital components—such as the intake, EGR and intercooler to name a few.
Internal combustion engines by design create positive crankcase pressure. This adds what is known as ‘blow-by’ into the engine’s crankcase. With modern vehicles, due to complex emission systems, this blow-by can’t simply be vented to the atmosphere like in the bad old days. GQ Patrol owners, I’m looking at you…
The modern solution is to feed these harmful blow-by gases—which contain such friendly byproducts as vaporised oil, NOx, hydrocarbons, carbon monoxide and water condensation—back into your engine to be burnt a second time.
What is a oil catch can?
Put simply: A catch can is a filtration device fitted between your engine’s crankcase breather and the air intake. Its job is to “catch” oil vapour and contaminants from engine blow-by before they can re-enter your intake system and cause carbon buildup.
How does it work? (The analogy)
Feeding those gases back into the engine sounds awesome in theory. However, as a mechanic mate once eloquently told me, it’s mechanically the equivalent of breathing in your own farts.
Not ideal for the longevity of your engine. This is why people fit catch cans to modern turbo-diesel engines. They filter and store as much of these oily diesel farts as possible, instead of feeding them back into your engine.
It’s not just oil: dealing with condensation
Something else I’ve noticed is the amount of condensation catch cans retain in cooler weather. This is especially noticeable with vehicles that do loads of stop-start driving, not allowing the engine to get hot enough to burn the condensation off.
The contents of the catch can would look absolutely putrid. More like a jar of mayonnaise that had been left in the sun. I’d rather see this gloop (that’s the technical term) captured in a catch can instead of being fed through your engine’s intake system.
Are catch cans worth it?
The short answer is yes. This is especially true with brand-new vehicles. Fitting a catch can from day one will give your engine the best chance of living a long healthy life. Think of it as preventing artery-blocking cholesterol buildup by eating healthily from an early age.
If you have an older vehicle, you might need to clean your intake manifold first (a dirty job, ask me how I know), but fitting a catch can afterwards will stop it from clogging up again.
Pros and cons of fitting a catch can
| Pros | Cons |
|---|---|
| Prevents carbon sludge buildup in intake | Requires maintenance (draining oil, changing filter) |
| Extends engine longevity | Initial purchase and install cost ($200-$500) |
| Can improve long-term fuel economy | Cheap/poor quality units can cause pressure issues |
| Keeps intercooler efficient (oil-free) | Installation space can be tight in modern engine bays |
How to pick a quality oil catch can
Not all cans are created equal. In fact, fitting a cheap eBay special can actually damage your engine if it restricts flow too much. Here is what you need to look for:
- Pressure Relief Valve: This is non-negotiable. It opens if the filter gets blocked or crankcase pressure spikes, preventing blown engine seals. The best players in the industry, like Ryco, include them for a reason.
- Quality Filter Media: You want an internal filter that actually separates oil from air, is easy to inspect, and cost-effective to replace. A hollow can or steel wool stuffing won’t cut it.
- Complete Fitment Kit: Look for solid mounting brackets, quality hose clamps and sturdy oil-resistant hoses that are large enough diameter to not impede flow.
Maintenance: Do you need to service them?
The best way to think of the filter inside a catch can is as a towel. A towel will absorb water, but has a limit. Once the towel has soaked up as much water as possible, it will begin to drain off the towel.
Most manufacturers recommend changing the filter out every 40,000km as a guide. Replacement filters will cost roughly between $80 – $180 depending on the brand.
I’d also have your mechanic check the condition of the filter (or check yourself, it’s not a hard job), clean out the catch can and drain the oil from the unit every service to keep on top of things. Speaking of draining, good kits come with a drain valve so you can empty the waste oil quickly without removing the whole unit.
Where to buy a catch can
Sticking to Ryco is the safest bet to ensure you get that vital pressure relief valve and quality filtration media. You can find their vehicle-specific kits at major auto retailers:
- Check Ryco catch can prices at Supercheap Auto
- Browse Ryco catch can kits at Outback Equipment
- Learn more at the official Ryco website
Note: Ensure you select a kit specifically designed for your vehicle’s engine make and model for the correct hose fitment and mounting brackets.
Frequently Asked Questions
What does a catch can do?
A catch can filters oil vapour and contaminants from the engine’s blow-by gases before they can re-enter the intake system. This prevents sticky carbon sludge from building up in the intake manifold and EGR valve.
Are catch cans worth it for diesel engines?
Yes. For modern common-rail diesel engines with EGR systems, a catch can is essential to prevent carbon buildup that can restrict airflow, reduce performance, and lead to expensive cleaning bills.
How often do you need to empty a catch can?
It is recommended to drain the oil from your catch can at every service interval (usually every 10,000km). The internal filter should typically be replaced every 40,000km, but always check the manufacturer’s specific guidelines.
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