We recently posted an article about suspension bushes, likening them to the cartilage in human knees. If that’s the case, then your car’s air filter is the equivalent of our lungs.

Today, we’re going to take a look at the lifespan of an air filter and how important its job is.

If you think about how you’d get on without your lungs, it should give you a fair idea of what’s coming!

So, when should you replace your air filter?

According to our research, you should change your air filter every 15k to 30k miles. However, each manufacturer has specific guidelines, so we’d suggest you check your car’s user manual or handbook for the correct duration for your make and model.

The mileage between replacements can vary depending on the type of driving you perform and where. For example, if you regularly drive in dirty and dusty environments, your air filter will likely work twice as hard as usual.

In those situations, you’ll need to replace it far more regularly. To achieve the level of operation your engine needs, keeping it healthy and at its prime performance, a clean and unclogged air filter is a must.

3 years, at the most

If you’re a low mileage driver, there’s a different set of rules to follow. Because air filters age—even without use—they lose performance over time, even without a single speck of dust passing through them.

Air filters go brittle over time, and it doesn’t take all that long either. As time passes, they become prone to cracking and tearing, and as the compound dries out, they become more delicate.

Those tiny holes and gaps in a filter’s structure provide the passage that dust and dirt particles need to infiltrate your engine. In turn, they add wear to the sensitive moving parts you’re trying to protect.

Even if your car’s been sitting in the garage for the past three years, you should consider replacing the air filter if you’re going to drive it again.

What elements affect air filter deterioration?

Your vehicle handbook might suggest different mileages for different types of driving.

City driving, or driving in busy towns with a lot of congestion, means that there are considerably more pollutants in the atmosphere around your car.

The same goes for dusty roads and tracks in the countryside, bumping up the quantity of dirt and dust trying to get into your engine.

It’s also worth considering the weather. As we previously pointed out, the air filter material is prone to ‘drying out’ over time, becoming fragile and vulnerable to wear and damage, so driving continuously in hot conditions can also limit the lifespan of your air filter.

Checking your car air filter

Competent home DIY mechanics will find it relatively easy to remove a filter and check it for damage or clogging. Most filter boxes are secured with a handful of screws or even clips that don’t require any tools.

A simple rule of thumb is if you lift your air filter to the light and the light can’t pass through it, it’s time to replace it.

A dirty air filter is usually fairly obvious. They tend to be covered in dark, dusty soot-like powder; the heavier and darker, the more likely it needs replacing.

If you’re not keen on removing filter covers, casings, or any other part under the bonnet, you can have your air filter checked regularly during vehicle services and other inspections.

The air passes up through the filter from underneath, so you’ll tend to find the biggest chunks of grit or gravel in the bottom of the filter box. If you are happy to check your air filter yourself, it’s a good time to clear the box of any grit, gravel or dirt trapped underneath the filter.

Let’s get back to the air filter being your car’s lungs…

Your engine needs to mix air with its fuel to provide the correct mix for the ignition process. Unfortunately, if that air is full of dirt and dust, it’s only a matter of time before the delicate components within your engine will wear out and stop doing the job they’re there to do.

So, just as your lungs filter the air that ends up in your blood, your air filter removes all the impurities harmful to engine performance.

If your car’s chugging and choking to perform as expected, that’s just how you’d feel in a dusty old cellar, stood in a smoky room or too close to a fire.

At least when your air filter needs replacing, you won’t need the expertise of a surgeon! Instead, your friendly Fixter mechanic will be more than capable.

Symptoms of a dirty or clogged-up car air filter

  • A lack of power under hard acceleration or at high revs
  • Poor fuel economy
  • The check engine light illuminates on your dashboard
  • Problems starting your car
  • Engine misfires
  • Unusual vibrations and engine sounds
  • Sooty smoke discharge from the exhaust
  • You smell petrol when starting the car

A choked-up air filter prevents the required air from reaching your engine. Imagine it wheezing and trying to suck in the air it needs, almost like it’s got a mouth stuffed with a pair of old socks or a gag. Your spark plugs can clog up without the correct dose of clean air, preventing them from delivering a healthy, powerful spark. Without that, you’re bound to have drive and ignition problems.

Clogged plugs cause a failure to ignite all the fuel delivered with each revolution. This can mean unburned fuel passing through the exhaust—hence that smell of petrol some drivers detect.

The knock-on from an engine working harder is that it burns more fuel than it needs to achieve the same performance. Burning more fuel results in a poorer fuel economy; if your mileage between fuel stops seems a little higher than usual, give your air filter a quick check. It could be that simple.