Those who have a basic understanding of how an internal combustion engine operates know their car needs fuel in order to operate. What they may not realize is that the fuel mixture in a car contains more than just gasoline. Yes, every non-electric vehicle on the road today requires trips to the gas station in order to work properly. However, gasoline is only half of the equation - cars need oxygen as well in order to run properly.
Before the air can be mixed with the gas inside the engine, it first needs to get inside the vehicle. This is why all cars have a grille on the front to allow air into the engine compartment. Rather than have drivers fill up on oxygen when they visit the gas station, the automobile simply uses the air around the car to run the engine.
Yet the grille presented early engineers with an issue. Air gets into the engine, but so does dust, debris, small rocks and other harmful components that shouldn't be inside. In small doses, this isn't a major problem. Over time, however, these small particles could eventually build up and ruin the engine completely.
The solution is the air filter. This is essentially just a screen that blocks dust and debris from getting into the engine, while allowing air to slip through. The only issue with air filters is that over time, these particles will clog the air filter. Some air filters become so thoroughly blocked up that no air can get through - and that can have serious implications for the engine.
Fortunately, air filters are both affordable and very easy to replace, even for amateur mechanics. The air filter is always located between the engine itself and the grille, but it may vary in shape. Most modern fuel-injected cars have rectangular air filters, while older carbureted engines use circular ones. The filter also tends to be inside a housing of some kind, and drivers may need to remove a few screws to access it.
Checking the air filter is rather simple - just hold it up to the sunlight. If you can see through the filter relatively clearly, it probably doesn't need to be replaced. Don't freak out if there's a couple of larger chunks on the filter, either - these can actually block smaller particles from getting through and improve performance. If the filter is completely caked with gunk, however, it's time for replacement.
The easiest way to do this is to simply take the air filter over to your local auto parts store. This way, the employees can match the new filter with the old one to ensure everything works and fits correctly. It's actually fine to drive a short distance with no filter installed, although this is certainly not a habit you'll want to get into. A short trip to the store won't ruin your engine, however.
There's nothing special you need to do to replace the air filter - just pop it in right where the old one was. In fact, you can probably do this right in the parking lot of the store, so you can be sure your new air filter is doing its job on the ride back home.