In the modern world and with high compression/low emissions engines, such as diesels, many owners choose to fit a catch can to their vehicle. This often leaves owners and mechanics alike wondering why manufacturers with the might of Toyota, Nissan or Isuzu would choose to omit them in the first place.
Catch cans are a simple piece of equipment used to capture excess oil vapour from the motor and prevent it from entering the atmosphere or re-entering the intake of a car.
This excess of vaporised oil, while not dangerous in small amounts, can cause long term issues with cars as it is passed through the engine. As the oil vapour passes through the intake and into the engine, it sticks to various components and often turns into sludge, which can block the intake and damage components, causing reduced power and poor fuel economy along with many other issues.
However, in a catch can, this vaporised is passed through an extra stage before being recirculated where a fine steel wire filter or similar device separates the oil from air and catches it where it can be drained from and disposed of.
Seeing as catch cans are so beneficial, why don't any cars come factory fitted with them? Especially when these systems can help improve the lifespan of a car tremendously.
The answer is two-fold and also covers one of the reasons preventative maintenance can be extremely beneficial.
The first and easiest to understand is cost cutting. While this may seem strange, due to the relative ease and low cost a manufacturer would have in including this system on each vehicle.
The simple fact is that these systems cost hundreds of thousands of dollars to engineer at scale and can cause a car to take longer and be more expensive to manufacture.
The second reason comes down to consumer satisfaction. Even though a catch can might be addition to your car, most manufacturers want you to be as happy as possible and attempt to make their vehicles as simple and easy as possible to live with.
A catch can is simply an inconvenience to most owners as they need to be drained regularly, increasing the frequency you would have to visit the dealership or the responsibility each owner would have day to day.
Overall, there is a fairly good reason for almost any modern car to incorporate a catch can, and with so many aftermarket options available, it's never been easier to find the right fit for your car.