from youtube
An air filter is made of cotton, paper, or gauze. This material must trap dirt and still allow air to pass through. Air filters don’t trap 100% of dirt particles but around 99% of particles are usually filtered out. New filters generally keep out less dirt than older filters. The new filter must first develop a dust film which makes the holes in the filter smaller and allows it to trap more dirt.
When too much dirt develops in the air filter, the air flow into the engine will suffer and it will need to be replaced. Not changing the air filter can reduce the engine’s performance and decrease the MPG of the vehicle. You can replace your air filter with a direct paper replacement or you can upgrade to a performance air filter.
K&N Filters (more…)