Pleated paper filter elements are the nearly exclusive choice for automobile engine air cleaners, because they are efficient, conveniently, and cost-effective.
The "paper" term is somewhat misleading, as the filter media are considerably different from papers which used for writing or packaging, etc. There is a persistent belief amongst tuners, fomented by advertising for aftermarket non-paper replacement filters, that filter papers flow poorly and thus restrict engine
performance.
In fact, as long as a pleated-paper filter is sized appropriately for the airflow volumes encountered in a particular application, such filters present only trivial restriction to flow until the filter has become significantly clogged with dirt.
