Vspec24

Vehicle is a '12 C350 coupe. This morning I figured I check to see how dirty my air filter is. Upon opening up the intake box, I saw one corner of the air filter stained with oil. I took out the filter and took a look inside the intake box and found a small puddle of oil. I then decided to take out all the pieces from the intake box to the throttle body and clean them thoroughly.

My question is this a common issue? I did some research and all I found is that there can be some traces of oil that may travel up the PCV from the crankcase. Is this true? Is it possible to cap off the breather tube that leads to the intake pipe?

Ausmbtech

Don't block off the PCV!!
There will be a small amount of oil in the intake, it's normal and nothing to worry about.

Vspec24

Thanks, good to know. I just find it weird that Mercedes has a system where oil travels into the intake system.