• car servicing

What types of filters are used in cars?

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Updated 27 Aug 2019

Rowan Johnstone

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Your car requires many different filters to prevent junk and unwanted material getting into its important bits and causing damage. In short, filters let the good stuff get in, but keep the bad stuff out. However, if you let too much bad stuff build up on your filters and they clog up, then they’ll end up not letting anything in at all.

Still with me? No filters equals bad. Filters in for too long also equals bad.

This is where routine maintenance comes in. Getting the various filters routinely replaced per the manufacturer’s recommendation is the easiest way to ensure your car is getting the right amount of good stuff and zero amounts of the bad stuff.

So what are these filters that need to be replaced?

Cabin filter
The cabin filter is responsible for filtering the air that goes into the air conditioning system, preventing dust and other unpleasant things from entering the cabin. These generally need to be replaced every 15,000 - 25,000km. However, it could be less or more depending on the vehicle and your driving environment.

If you’re part of the exclusive electric vehicle (EV) owners’ club in Australia - and there are only about 6,000 or 7,000 of you - then this is the only filter that you need to worry about.

Engine air filter
Every internal combustion engine requires air in order to make power. They don’t just want any old air though, it needs to be filtered to remove any abrasive or harmful particles from getting inside. This also helps to improve fuel efficiency because the higher the quality of air the engine gets, the more efficient it becomes.

If the engine air filter becomes clogged up, it could restrict airflow into the engine which won't do any favours for your fuel efficiency, or your engine. Your engine air filter should be replaced ever 25,000kms or so, but your manufacturer will specify exactly when yours should be replaced.

Fuel filter
Fuel filters are located either inside your fuel tank or in the fuel line before the fuel rail. Its job is to make sure that any dirt and debris inside your fuel tank does not come into contact with your fuel injectors. If this stuff was to get to your injectors, your car won’t be as fuel efficient or perform as well as it should.

The best place to look for replacement intervals is your owner’s manual but, generally, fuel filters have replacement intervals of 45,000 - 55,000kms.

Oil filter
Getting your oil filter changed, along with your oil, is the staple of car servicing. It should be the absolute bare minimum of any car service and needs to be done roughly every 10,000 - 15,000kms or 12 months. Similar to the other filters, the oil filter prevents harmful materials from going where they shouldn’t.

Engine oil is used to lubricate the various, extremely important moving parts within your engine. Without this lubrication, the friction caused by the components rubbing against each other not only wastes energy but could cause a significant amount of damage. A small amount of friction is inevitable, however, and over time tiny metal particles are released. If these are left unchecked, they could block the flow of oil throughout your engine.

It’s the oil filter’s job to contain them and prevent them from getting in the way. Eventually, the filter will become clogged so the rule of thumb is to whack a new one in when you change the engine oil. That way, your new oil can flow unrestricted through a clean filter.

Diesel particulate filter
The diesel particulate filter (DPF) bucks the trend here. Instead of preventing bad stuff from getting in, it prevents bad stuff from getting out. DPFs are only found on diesel vehicles manufactured from 2007 and is a direct response to tightening emissions regulations. The role of the DPF is to prevent harmful carbon particulates produced in the combustion process from entering the atmosphere.

The DPF traps these particulates until a certain saturation level is reached. Once this level is reached the exhaust temperature is increased to ‘burn off’ the particles. The aim of the game here is to reduce diesel emissions from the vehicle by around 80%. A well-maintained DPF can last you 200,000kms or more before it needs to be replaced or cleaned.

So there are all your filters and the reason why your car has them. In nearly all cases they’re cheap parts to replace and the job isn’t that involved, so there’s no excuse to neglect them. Whilst you should get a qualified mechanic to complete all work on your car, it is especially recommended when replacing the DPF or fuel filter as these are more involved tasks where the experience and training of a quality mechanic is needed.

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Written By

Rowan Johnstone

On weekdays Rowan can be found in the AutoGuru office, driving content and growth with the rest of the marketing team.

On weekends you’ll probably find him in the garage with his dad restoring a 1958 Ford Star Model Customline or enjoying a cruise through the Gold Coast hinterland on his Suzuki GSX-R600.

Despite his passion for being behind the wheel (or handlebars), he looks forward to the day when he can commute to work in his own driverless car.