After some more research, it looks like that black plastic part is the breather cover. But I’m wondering if the oil is actually leaking from there, or if it is leaking from the cam seal higher up. Is there any way to tell if the leak is coming from the cam seal without taking the whole engine apart? I have 187,000 miles on this Civic and the timing belt and tensioner was replaced at a Honda dealership at 114,000 miles. I’m not sure if the cam seal was replaced then or not.