• Paper filters. The first type is the widely known and equipped-from-the-factory paper filter. Don’t let the word “paper” fool you, it’s not the biodegradable paper that we can easily throw away. This paper is of an industrial quality and pleated in an accordion fashion to increase surface area. This means that there’s more space for dirt to become trapped. According to tests, these filters decrease fuel efficiency and engine power. Some say that this is not true unless the filter is significantly clogged. These filters are relatively cheap and easy to replace, but replacement must be done more frequently than some other filter types
• Foam filters. These are an aftermarket filter that can be bought from a wide variety of retailers. This type of air filter is very popular with those who either live in dusty areas and/or partake in sports such as off-roading and rally racing. The foam is a polyurethane soaked in an oil. They come in different grades of foam and can vary in thickness as well. These two factors contribute to the airflow resistance and the dirt capacity
• High performance filters. High performance filters are typically made of a cotton gauze and are more popular among those who own vehicles such as sports cars, road-rally cars, competition trucks or those who just want to increase their air intake and power of their engine. These filters can be a bit pricier than the others, especially if bought with a cold-air intake system. These are an aftermarket filter that can be bought from specialty dealers
• Oil bath filters. This was what was used in vehicles until the introduction of paper filters in the 1960s. This messy filter consisted of a pan of oil, over which an insert of fiber, paper, mesh or similar material was fitted. Incoming air flows rapidly over and around a serious of turns. The air must take a turn at high velocity over the oil pool where the heavy elements of the air contaminants are unable to make the turn and are captured by the pool of oil. The lighter particles that make it over the oil are captured by the insert. These obviously aren’t popular and are considered obsolete because they are a messy hassle to change