How to Check Your Vehicle's Air Filter
In most newer, fuel-injected vehicles, the air filter is found inside a rectangular box called a cold air collector box. The air filter is usually close to the front of the vehicle, near the inside of one of the fenders. Air that’s scooped up by the front of the vehicle moves through an air intake tube into the air filter inside the box.
On older fuel-injected engines and carbureted engines, the filter is found in the air cleaner, which sits atop the engine. As you can see here, it’s large and round with a snorkel sticking out of the side to facilitate the intake of fresh air.
Your owner’s manual should have instructions on how to locate and get at your air filter.
To find out if your air filter needs to be replaced, just lift it out (it isn’t fastened down) and hold it up to the sun or to a strong light. Can you see the light streaming through it? If not, try dropping it lightly, bottom-side down, on a hard surface to jar some dirt loose. (Don’t blow through the filter — you can foul it up that way.) If you drop the filter a few times and it’s still too dirty to see through, you need a new one.
Because the air filter extracts dirt and dust particles from the air, you should change it at least once a year or every 20,000 miles, whichever comes first — unless yours gets very dirty before then. If you do most of your driving in a dusty or sandy area, you may need to replace your air filter more often.