There are a couple major filters in your car. The engines air filter, fuel filter and the interior cabin air filter. The interior cabin air filter works much the same as the air filter in your furnace at home. It collects dust and helps to keep dirt from being spread throughout from the heating and air conditioning vents. The same goes for the car vents. So breath dirty air or change the filter every 20K miles and breath filtered air.
The Engine needs clean air for two important reasons, both can save you money in the long run. First off, the engine needs clean or to prevent dirt and debree from entering the internal part of the engine that could cause serious damage to components. Second, the more air that comes through , the better the engine can perform and give you better fuel mileage.
The fuel filter keeps impurities in the gas form entering the fuel lines and preventing the fuel injectors from clogging and allowing the injectors to spray that fine mist that gets you better fuel mileage.
Crankcase Vent Filter:
Prevents dirt from entering crankcase.
Cabin Air Filter:
Keeps abrasive dust, dirt, bugs and other foreign matter out of the engine air intake.
Engine Oil Filter :
Traps dirt, metal filings and sludge, allowing only filtered oil to circulate through the engine.
Collects dirt and metal filings, protecting finely machined parts.
Traps rust, sediment, dirt and other particles which may enter the fuel system and clog tiny jets.
Collects gasoline vapors and returns them to the fuel system.
Proper fluid levels and clean filters are vital. In addition to the grit, dirt and other foreign matter which enters the engine and transmission from outside air and other sources, your car also creates its own contaminates through condensation, chemical reactions and wear. Some components would self-destruct if they were not protected by filters.