Air filters, as far as automobiles are concerned, are used to prevents contaminants and particulates from entering the engine. Lack of an air filter or a bad one could cause in premature wear and tear as well as oil contamination, lowering engine performance and fuel efficiency greatly. Since the quality of air is important in internal combustion engines, air filters are vital in keeping the performance of any automotive vehicle.

Prior to the 1960s, oil bath filters were the industry standard for air filter application. It consist of a round bowl filled with oil and a round insert containing fiber, foam and other coarse materials. The idea is to make air flow go through a maze with large particles being unable to reach the engine due to the loss of momentum and fall into the oil, and smaller particles to get caught by the materials contained inside the round insert. While the setup actually works, maintenance is often messy and inconvenient, which led to the phasing out of the application, save for off road vehicles and engines. Other problems faced by oil bath filters is the increase in exhaust emissions, as well as the relative size needed for the device to be actually effective.

With the advent of fuel-injected engines, most cars use pleated paper filters shaped as a flat panel. Cars that still use carburetors or throttle body fuel injection configurations use a cylinder-shaped air filter, placed on top of the carburetor or throttle body and covered in either plastic or metal to regulate air temperature.

Pleated paper filters, are usually the stock air filter for most cars and eventually replaced oil bath setups. Of course, the misconception is that the paper in this case isn't actually the same as the writing medium or material for books used. While cost-effective, efficient and easy to service, pleated paper filters will eventually need replacement, as air flow will be restricted once it gets excessively dirty.

Given the limitations of paper air filters, certain companies and tuner enthusiasts have looked to a more potent material or application in air filtration and cleaning. The aftermarket scene has many brands and companies that provide adequate alternatives, but also upgrades to stock filters. Some brands like True Flow air filters specialize in producing performance air filters and other True Flow performance parts, like their air intake systems, which are usually connected to air filtration.

Most True Flow air filters usually use treated Foam as their material of choice for air filtration. Unlike pleated paper filters, foam filters allows air to flow through despite getting clogged from dirt and debris. True Flow air filters in particular, use reticulated foam and is treated with a specially formulated solution that makes dirty and dust stick to the filter. The construction of the foam is also a lot thicker than paper filters, approximately 16 timers thicker, in order for the foam to capture more dirt and thus needing less maintenance compared to its pleated paper counterpart.