Why You Need to Change Car Filters

No matter what’s flowing through it—air, oil, transmission fluid, or fuel—nearly every car filter works the same way.

Filters rely on a permeable material called the filter medium (often paper, though cotton and foam are also sometimes used) to remove and trap particles. The filter medium has a dense structure filled with tiny holes. The size of these holes depends on the fluid and the filter, but they are usually microscopic. As air, oil, or fuel flows through the filter, particles hit the dense filter medium and get stuck. Dust, dirt, and shavings stay in the filter, while the fluid or air flows through the holes. Because the filter is trapping these particles, it will eventually get full of dirt and contaminants. When that happens, fluid and air flow is restricted and can eventually become blocked. When the flow is restricted too much, it’s time to replace or clean the filter.

Want an example? Plug your left nostril, then try to breathe through your nose. It’s not as easy, is it? That’s what your engine is trying to fight against when you need to change your air filter and what your oil and fuel pumps are struggling against when those filters become clogged.

What happens? Your engine can’t circulate its essential fluids, and that means vehicle performance diminishes. Your engine can’t breathe, so you need to use more throttle to compensate. You have less power and use more fuel to get less acceleration.

If your oil pump is straining against the filter, oil might not be able to get to crucial components like valve lifters, variable valve timing mechanisms, or your engine bearings. The result is poor performance and a higher chance of those parts failing.

Likewise, if your fuel pump is struggling to send out enough fuel, it can burn out. It can also starve your engine of fuel, giving you less power, hurting drivability, and possibly even preventing the car from starting.

What happens if your filter gets clogged and you still don’t change it? Plug both nostrils and try to breathe. Not good, is it? Nothing flows through, and your car doesn’t work its best. Many filters have a bypass mechanism, preventing complete oil or fuel starvation. But when the filter is bypassed, the fluid is no longer being filtered and your vehicle isn’t protected.

Keep in mind, some vehicles have cleanable reusable air filters. They usually use a layer of oil to trap dirt. These don’t clog, but they do stop filtering with prolonged use. So, servicing them at the recommended intervals is essential to avoid engine damage.

That depends. Best practice says oil filters should be changed with every oil change. Air filters and cabin filters are often recommended to be changed once a year. No matter the filter, harsh conditions like dirt roads can require more frequent changes.

The best way to find out? Check your owner’s manual or speak with a NAPA Auto Parts professional. They can tell you when your filter needs changing and send you home with the right parts for your vehicle.