One of the simplest pieces of maintenance that amateur mechanics can perform on their own is changing the air filter. Your car needs oxygen in order to run properly, and it's important that your vehicle gets as much as possible. However, the grille on the front of your car also leaves your engine to all sorts of dust and debris particles that can be harmful over time.
The solution for this is an air filter. Basically, this screen lets oxygen in and keeps debris out. The problem is that the dust and dirt particles build up on the filter over time and begin to clog it. Over time, this can stop the air filter from doing its job, as no air will be able to get through. Lack of oxygen in a vehicle's engine leads to reduced performance, poor fuel economy and can wear out the engine over time.
Thus, drivers will want to change out their air filter from time-to-time in order to stop these particles from building up. There's a lot of debate over the best time to change an air filter, and it really varies depending on where you drive. If you're on dirt or gravel roads quite often, it's not unheard of to change the air filter multiple times per year. If you drive primarily on highways and paved roads, then you can probably go for a year or more without needing to swap out the air filter.
Locating the air filter is relatively simple once you have the hood of your car open. The housing for the filter is typically located on top of the engine, or somewhere between the engine and the grille. On newer, fuel-injected vehicles, the casing will be square or rectangular. Models with carburetors will probably have a circular unit for the air filter. You need to open up the housing, but this too varies from car to car. Some might be able to be opened by hand, while others will require a screwdriver to get the top off. Be sure to keep any screws or nuts in a safe place if you do have to take them off.
Once you've found the air filter, take it out and hold it up to the sunlight. If you can pretty much see through the filter, then you probably don't need to replace it. Some drivers will replace their filter at the first sign of any dirt or grime, but this can actually be detrimental. Large chunks of debris that get caught in the filter actually serve to keep out the smaller particles and can improve performance. A filter is not performing at it's best right out of the box - it's usually a little better at blocking particles once it has a few stuck onto the framework.
If your filter is especially dirty or grimy to the point that air wouldn't get through, however, then it's time for a replacement. Most auto parts stores should sell air filters, and they're not expensive. It's a good idea to take your old air filter (preferably in a plastic bag if it's really caked with dust) to the store with you. This way, the employees can help you locate the exact replacement.
Although some drivers might be hesitant, it's okay to drive to the auto parts store with no air filter installed. If you think about it, plenty of oxygen will be getting into your engine with no filter - a few particles may as well, but nothing that would be a cause for major concern. Just don't make a habit out of it.
Head home, pop your new filter where the old one was, and sit back and admire your handiwork.