Your Toyota Matrix has two air filters -- an engine air filter and a cabin air filter. They're both more important than they seem. What does an air filter do, generally? How does each of yours work? Your engine filter traps airborne particulate like dirt and dust. Your cabin filter captures allergens like pollen. They do their jobs using either cotton, synthetic paper, or foam fibers, with a specially pleated design to catch it all better. If that hatchback you love to drive didn't have either filter type, those contaminants would build up. They'd cake onto engine parts like your throttle body's air intake, your fuel injectors, and even your spark plugs. They'd accumulate throughout your HVAC, too. When that happens, they start to wear out those parts and systems double time. Luckily, there's an easy way to keep all this from happening. Just change your air filters regularly. Unfortunately, though, even OEM air filters can decay with age or clog. If they get too blocked up, more trouble results -- everything from increased engine emissions and lower gas mileage to engine stress and misfires. Even your heater and air conditioning can malfunction. So, when exactly should you replace air filters? Consult your owner's manual for the best answer. Otherwise, you usually do it about every 12,000 to 15,000 miles. It's best to look for the signs it's time. They include a Check Engine light, gunky and worn-out fibers, strange engine noises, bad cabin odors, and too much exhaust smoke coming from your tailpipe. If you see these symptoms, you can buy new air filters right from the factory. Just be sure to order genuine. Air filters from Toyota, after all, will fit your Matrix best. You can get them right here online at our auto parts store. Order today!