Words: Alex Rae
If you check the cost of replacing the air filter on your last service at a mechanic you might be surprised to learn how much you can save. Replacement air filters cost from $20-$40, depending on the make and model of car, which compares well to a friend’s recent service that charged almost four times that (with labour).
If you’re up for saving some money, getting your hands not too dirty and keeping your car breathing clean (the air filter is the guard between the atmosphere and the inside of an engine), then follow this step by step guide to changing an air filter.
How long will it take?
If you already have the new filter ready to go and all of your equipment, then it should take less than 30 minutes to change the air filter in your car. If you’re new to getting your hands dirty under the bonnet, then check the owner’s manual to quickly and easily locate the air filter.
What is a car air filter?
An air filter is a device to remove/filter dust and other foreign objects from the air before it enters the air-inlet of an internal-combustion engine. There are two types of air filter, one for the engine and one to ‘purify’ the air before it enters the cabin, this article is not about the latter type of filter. Car air filters are made from a very heavy type of porous paper (to allow air to flow through but not grit) that’s been pleated to increase the surface area.
What does an air filter do?
The air filter is responsible for keeping dirt and debris out of the engine, a very important role, as even the smallest debris once inside the cylinder chamber can act as an abrasive and, at worst, cause engine failure. A dirty air filter won’t necessarily be any less effective in keeping dirt out but it will restrict airflow into the engine and will thus increase fuel consumption. The OEM (original equipment manufacturer) air filter is usually made from breathable fibrous paper material.
How often do I need to change my car’s air filter?
It’s important to regularly perform a maintenance check on your car and the owner’s manual will specify when the air filter needs to be changed, however, a good practice is every 12 months or 15,000 kilometres. If you live or drive in certain conditions, say on dirt roads, the frequency will be more often, say, around 5000-10,000km. That said, if you’re travelling on particularly dusty roads, according to our technical editor Robert Pepper, then it might be necessary to shake out the air filter at the end of every day.
How do I know when to change the filter?
Checking that it needs replacement is as easy as observing the amount of dirt stuck on the intake (exterior) side and when it looks dirty or if it’s damaged, it needs replacement. Do not drive without the air filter in place and head to your nearest car parts shop to buy a new one.
How do I check if the mechanic changed my car’s air filter?
This is very easy: if the filter looks clean and bright and there’s no dust in the air box then it’s very likely the mechanic has indeed replaced the air filter, whereas a used, dirty air filter looks just as described.
Are all air filters the same?
Nearly all standard replacement filters will be similar to the OEM item but there are alternatives available made from materials such as cotton fabric. These filters promise the same effective protection from the environment but can allow more air through and are reusable after a wash. Although they do cost more, some promise they will last the life of your car if regularly maintained. In most instances, these filters come in the same size as the OEM filter and fit straight in.
A note on pod type filters: Some high flow or reusable type filters come in a pod shape and, unless an OEM replacement part, these are not made specifically for the vehicle and are designed to be attached by altering the intake system. Changes to the engine can be illegal and insurance companies may not cover the vehicle. It’s always best to not modify the vehicle without consulting a professional and the relevant road authority or police if unsure of legalities.
How do I choose the right filter for my car?
Head into your local car parts store and look up the make, model and year of the vehicle in the air filter parts directory or ask for assistance. It’s that simple. Research this subject on the Internet and you’ll read all sorts of stuff about why you should spend as much money as you can on an air filter rather than just plump for the cheaper OEM version. The more expensive air filters will generally be reusable which is great for the environment but of little benefit beyond that. Where the more expensive air filter manufacturers try and differentiate themselves is by saying that the engine will produce more power when using their filters, but there isn’t a single study that’s proved any reasonable performance improvement to justify the extra expense, so, stick with the OEM variant and don’t be swayed by a salesperson trying to upsell you.
How to change a car air filter
1. Removing the old air filter
The air filter resides inside the airbox, usually a large rectangular shaped box on either the right of left front of the engine bay. If unsure, refer to the owner’s manual.
Nearly all airboxes have a lid that’s held on by metal clips, but some may be held in by screws and will require a screwdriver. Unclip the lid and gently move it out of the way, making sure not to disrupt the pipe leading into the engine. It some instances the airbox lid may need to be removed from the intake pipe. To do this unscrew the pipe clamp until it is loose and remove the lid.
The old filter can now be seen and will need to be popped out. If it’s stuck, use the butter knife or a spatula to pop it out. At this point, you can inspect the exterior side of the filter. It’s also a good idea to clean out the airbox, but do not stick the rag up the intake pipe as there can be fragile electrical components inside.
2. Fitting the new air filter
Simply place the new filter into the seat where the old one came out. Make sure it is facing the right way – usually the wavy side facing down or towards the exterior where air enters the vehicle.
Make sure the filter fits snug and it is not loose at all. It’s very important that no foreign objects can get through.
Replace the airbox lid and ensure it is clipped on correctly and is not loose. Once everything has been replaced, turn on the car and let it idle. It should sound normal with a smooth idle, if not there may be an air leak from a loose connection that will need to be corrected.
Remember: Buy the correct air filter for the make, model and year of vehicle. Do not try and cut or fit in a different size filter. Buying a reusable air filter may be beneficial, but make sure it is made to replace the original filter and is not a pod type shape. Never rush and never try to force any parts.