When it comes to ensuring optimum reliability in the contemporary turbo-diesel engine off road, there are two prerequisite upgrades to quality components. The first is extra, top shelf fuel filtration, the second is a great quality oil catch can. And if the second surprises you, you're not alone.
On turbo-diesels, little amounts of fuel sneak past the piston rings and into the sump. Crank case ventilation stops this pressure from amassing by letting it out into the air on older vehicles, and into the air intake where it's burned on newer vehicles. This makes the air messy with oil mist.
The catch can only does one job, but it's a big job.
A catch can's only job is to get the oil mist out of the air, so it can be reused or disposed of. They do not use any power or fuel, and they won't affect performance of your engine in anyway. What they do is reduce maintenance costs and stop reliability issues.
Modern turbo-diesel engines are highly-tuned beasts with plenty of a lot of sensors, valves, filters and pipes. These days most engines vent the crank case pressure into the air intake, just after the air filter, this air then runs through the turbo and intercooler via a few of pipes to the engine. While the turbo won't be too troubled by this small amount of extra oil in the air - the turbo temperature keeps the oil vaporised - as temperature drops thanks to the intercooler, the oil mist droplets form and sit on the intercooler's internal surfaces.
In no time at all those droplets will combine to cause trouble, partially blocking your intercooler and inlet manifold more enough to cause a drop in how your vehicle runs. You'll also find problems developing in your Mass Air Flow (MAF) sensor, which regulates fuel injection, because the oil build up will stop the sensor working properly.