AzCamel

I just changed my engine filter and notice there are 4? The non remove/replaceable one seems to be a charcoal one, am I correct in assuming it is not to be replaced or removed and just change the normal yellow/orange one?

glennhl

Yes. The charcoal one is permanent and is there to absorb gas fumes in order to meet emission requirements. Some people get rid of the charcoal filters.

AzCamel

Oh ok. I did not remove it, I doubt there is any performance gains that I would notice