When should you fit a catch can kit?

These days it’s quite common for people to recommend a catch can — and rightly so. Separating the oil from crankcase fumes is a great idea, as those fumes are responsible for a fair share of engine problems. But first, it’s important to understand a few things: why a catch can could be useful, when you should fit one, and what it can and can’t do to fix the issue.

Short answer: a catch can is a worthwhile second line of defence — but reduce the cause of blow-by first with a flushing oil and a quality fuel additive, or you’re only treating the symptom.

During combustion, a small amount of the burnt gases get past the piston rings (blow-by) and into the engine sump. That happens even in brand new engines, and for environmental reasons this excess sump pressure is directed into the air inlet system. Some oil vapour is carried with it, and that’s not a problem — until blow-by gets worse.

When blow-by becomes excessive, oil gets inside intercoolers and intake manifolds become fouled with oil and soot. Carbon deposits form inside the combustion chambers, especially around the piston rings, and this increases blow-by further. Performance deteriorates, and eventually engine life is shortened. Clearly, anything that increases blow-by needs to be addressed.

Should You Fit a Catch Can Kit?

Your first line of defence, before fitting a catch can, is to reduce the cause of blow-by, which in turn reduces oily crankcase fumes. Blow-by can also be caused by too much city driving, sticking EGR valves, turbocharger coking, faulty injectors, bad fuel, or malfunctioning emission control equipment — so the oily fumes that a catch can removes are not the only factor at play.

How to Reduce Crankcase Fumes Before Fitting a Catch Can Kit

Remove existing piston ring groove deposits using a flushing oil concentrate capable of dissolving and dispersing those tough-to-remove deposits, such as Flushing Oil Concentrate.

Then use a fuel additive that actively burns off carbon and keeps the top ring area clean, while also burning the fuel more cleanly to reduce exhaust soot production. There aren’t too many around, but FTC Decarbonizer is one example that actually works. (See our guide on how to fix engine blow-by for the full process.)

People who employ this first line of defence keep blow-by well and truly under control. They avoid inlet-system fouling while maintaining excellent reliability and low maintenance costs. There’s rarely a need to fit a catch can — but it certainly provides added protection.

Will a Catch Can Kit Reduce Crankcase Fumes?

An effective oil catch can (such as the Provent brand) is designed to remove oil vapours from the crankcase breather. It’s a waste of money fitting a cheap version that doesn’t do this properly. A quality catch can is excellent insurance against some expensive problems, and well worth fitting — especially when travelling remote. However, owners need to realise that catch cans are the second line of defence. That’s because they don’t address all the causes of blow-by — they’re a band-aid fix. Catch cans certainly filter out the blow-by gases, but they do not fix what is causing the fumes.

Catch Cans Prevent Expensive Repairs, but the Cause Remains

If you’ve identified excessive engine wear as the cause of the blow-by, you certainly need a Direction Plus catch can kit. A catch can is also recommended if you aren’t proactive in decarbonising your engine and maintaining clean piston rings, as it will help prevent some problems.

If you decide a catch can is good insurance and worth the expense, definitely buy only a quality one. Keep in mind that a catch can needs to be monitored and serviced correctly to keep functioning as intended. For help choosing, see our catch can comparison and our guide on spotting a fake Provent 200 filter.

If you have any questions about when to fit a catch can, give the team at Cost Effective Maintenance a call on 07 3376 6188.

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