Oil catch cans are incredibly common, especially on highly modified engines. On forums, you can find several roundabout answers ranging from ‘it helps keep your engine clean’ to proclaiming ‘it will prevent your engine from blowing.’ These vague responses are lacking in real answers as to what the actual purpose of a catch can is and how it functions to benefit your engine. This is a case where people are giving sound, albeit, uninformed advice. So what does a catch can exactly do?