Catchin’ Oil

Your diesel engine is slowly killing itself, but a Catch Can is a quick and easy solution

Low Range Episode 7 4WD Convoy

Modern diesels are a hell of a thing. They’ll fly down a dusty track faster than ever, sip fuel like it’s the last tank they’ll ever have, and pack a punch that’ll muscle around campers and caravans heavier than ever thought possible. While it’s often cause for Facebook mechanics to pipe up, they’re also not killing us any more thanks to a heap of high-tech emissions gear that cuts all sorts of nasties out so we don’t knock a year off our lifespan every time we walk past the tail pipe.

Problem is, the factory doesn’t always get things bang on. One of the biggest issue with any modern diesel engine is the EGR, or Exhaust Gas Recirculator. It’s a bit of engineering wizardy where the manufacturers have worked out that by introducing a precise amount of exhaust gases back into the combustion cycle they can drop cylinder temperatures just enough that harmful NOx gases aren’t formed. NOx is the bad stuff that causes smog build up in cities, causes breathing issues and in extreme cases can cause lung cancer. Bloody top bit of tech eh? Well sorta. Y’see the problem is those spent exhaust gases also contain diesel particulates, or soot. When those soot particles come into contact with your oil lined intake they begin to gunk up, choking your engine of air giving horrible fuel consumption, huge drops in power, and a heft repair bill. But an ounce of prevention is worth a pound of cure.


Now unless you can count your brain cells on one hand chances are you’re not pouring litres of fresh oil down your air intake, so how exactly is the clean side of your engine coated in an oily mist? The culprit is a little thing called blow-by. As the engine is cycled and the fuel ignited pushing the piston down, some of the pressure inside the cylinder is able to force its way past the piston rings pressurising the crank case as a result, it’s completely normal and even brand-new engines will have some amount. Given enough time that pressure will build up and start forcing oil out of seals and gaskets causing a hell of a mess. The solution is a PCV Positive Crankcase Ventilation valve; effectively a one-way valve that allows that built up pressure to bleed over and find its way back into the intake. As the pressurised air leaves the crankcase and travels into the intake it carries with it misted oil, this oil eventually builds up a thin residue all throughout the intake manifold, valves, cylinder head, and anywhere else that should normally be clean. When it mixes with diesel soot from the EGR things start turning pear shaped for your engine, which brings us too…

4WD Diesel Oil Catch Can


The issue is a combination of oil and exhaust fumes combining and turning into a thick paste all throughout your engine. Remove one of the ingredients and there’s no paste. Some people reach for the EGR blanking plates not realising they cause all sorts of long-term issues. They’re working against the tech, rather than with it, and with many environmental agencies pointing to how easy pollution systems are being removed it’s a short-term solution that could potentially land you in a whole heap of financial hurt and cause tougher and tougher emissions restrictions in the future.

By fitting an oil catch can the EGR system can work as it’s intended. The catch can simply fits inline into to the hose between the PCV valve and the air intake and filters out the oil removing the source of the oily residue. So, if it’s such a simple fix why aren’t they like that from the factory? Well, they are, but only in some vehicles. Many Euro cars and 4WDs have them stock, as do a whole heap of performance cars. It’s a little like a locker in that regard, a top-spec LC200 comes twin locked, but a base model HiLux doesn’t even though they’re just as beneficial in the HiLux. Manufacturers don’t like taking a hit to the back pocket, so unless it’s going to sell more cars, or prevent issues in the warranty period don’t expect to see it on the spec-sheet of a new 4×4.

4WD Diesel Oil Catch Can


Jump on eBay right now and you can find countless ‘Catch Cans’ for less than the price of a meat-pie and coke. So why shouldn’t you just buy one of those? Because they’re absolutely bloody useless. You’d be better off taking a $20 note out of your pocket and throwing it on the ground. There’s a few things to look for in a quality catch can, but the biggest feature should be that it actually catches the oil. Most of the cheap catch cans are little more than a slightly different sized hose. The oil-infused air pumps in one side and pumps out the other. Stuffing them full of steel wool might catch some oil but it’s a little like running a kitchen sponge as an air-filter. To actually separate the oil from the air you’ll need a filter or preferably a baffle system. The other major issue you’ll find with cheapies is they’re overly restrictive, either through the barbs into the can itself, or with smaller than factory inlet and outlet sizes; if it doesn’t allow the crank case pressure to properly vent your first indicator will be a driveway coated in oil and a whole bunch of gaskets that need to be replaced. A $20 catch can could cost you thousands.
Over time the catch can will fill with oil so it’s important to find one that’s easy to empty or drain too. The other major feature to consider is just how robust it’s constructed. The right catch can should be simple in design and strong in construction so you’re not chasing down oil leaks the first time you punt your pride and joy down a corrugated track. The Roo Oil Catch Can comes in an easy to install DIY kit but if you’re after more info or want to know what’s perfect for your 4WD give us a buzz here at Roo HQ and we’ll get you on the right track.

Buy the Oil Catch Can Online Here