What is a Diesel Particulate Filter (And Why Should I Care?)

Given its location, it’s no wonder you don’t know much about your diesel car’s DPF - if you even knew it had one to begin with! Knowing what your DPF is and why you should look after it is super important, and it could even save you money in the long run.

Read on to learn what a DPF is, if your car has one, and why you should care about it in the first place.

What is a Diesel Particulate Filter (DPF)?

Located in the exhaust of your car, a diesel particulate filter – or DPF – is designed to trap the soot that your car produces when diesel is burned. Without a functioning DPF, your diesel car would produce far more harmful emissions, which can cause respiratory problems if breathed in.

Though diesel cars produce less CO2 (Carbon Dioxide) than petrol cars, they also produce high levels of NOx (Nitrogen Oxides), making a diesel car less environmentally friendly than you might assume.

Does My Car Have a DPF?

If you own a diesel car that was built after 2009, then it will have a diesel particulate filter. As your car exhaust produces a number of harmful gases, it has to meet a certain standard so as not to severely impact air quality. This is dictated by the EU emissions standards - currently, petrol vehicles must meet Euro 4, whilst diesel vehicles must meet Euro 5 standards as of 2009, with Euro 6 standards being introduced for diesel cars in 2014.

Should I Buy a Car with a DPF?

This is really a question of whether you want your vehicle to run on diesel or petrol, as a petrol-powered car won’t be fitted with, or need, a DPF. There are pros and cons for both options. As of 2022, petrol vehicles seem to be maintaining their popularity, whilst the market share for diesel vehicles in 2022 was down from 25.2% in 2019 to 5.7%.

Electric vehicles are also becoming more popular, so it is definitely worth considering your priorities when it comes to the car you want to drive. As we all become more environmentally conscious, electric vehicles do seem to be paving the way for the future of the automotive industry.

Why Should I Care About My DPF?

As previously stated, your DPF has a vital role to play in limiting the harmful emissions your car produces. If you don’t care about your DPF, and look after it accordingly, then you run the risk of needing a DPF replacement much sooner than expected, which can cost as much as £3,000! Not only will this cost you time and money, but it may release those harmful gases into the air, and it could lead to an even more expensive repair if your blocked DPF damages your engine.

You should bear in mind that once your DPF is approximately 70% full of soot, you may notice a change in your car's performance. At 90% your car will need a full-on DPF replacement. If you remember to book a DPF clean approximately every 6 to 9 months, then you can give your diesel particulate filter the best chance at a longer lifespan.

How Can I Look After My DPF?

You can look after your DPF by being aware of the symptoms of active and passive regeneration, which your car goes through in order to burn off the trapped soot stuck in your DPF.

Regeneration is your car’s way of getting rid of the soot that your DPF has trapped, as this can impact your car’s performance. If you look after your DPF, by avoiding using the car at low speeds for short journeys, it can last over 100,000 miles.

Your car has built-in engine control software which can tell when your DPF is blocked, at which point it will trigger active regeneration by sending more fuel to the engine and raising the temperature of your exhaust. This usually happens when the soot level has reached a capacity of 40-45%, and this can be burned off in approximately 5 to 10 minutes.

Short journeys can block your DPF as there isn’t enough time for the regeneration process to complete, and low speeds won’t help your car reach the high temperature needed to start the process. Passive regeneration occurs when you drive at high speeds, as the higher temperature of the exhaust can cause a chemical reaction which neutralises the soot. You need to drive for at least 15 minutes at a speed of 40mph or more to start and complete the process. 

Is My DPF Failing?

If you notice an illuminated DPF warning light on your dashboard, or otherwise suspect that your DPF might be failing, then it is absolutely time to take your car to a professional garage and have this looked at. You should bear in mind that a low-quality service can actually lead to a DPF blockage in the first place.

That’s why it is always smart to have your diesel particulate filter cleaned by a skilled mechanic, who will be able to carry out a procedure called forced regeneration, in which leftover soot particles are burned away at a high temperature.

Important note: If you have any intention of removing your DPF yourself, or driving your diesel car without one, you should know that this is actually illegal in the UK! What’s more, if your car was fitted with a DPF when it was first built, then you will fail your MOT if your car doesn’t have one.

Best to leave it to the experts.

At BookMyGarage, you can book a DPF clean near you, and help your DPF resume its natural regeneration cycle. You can boost your MPG (Miles Per Gallon), engine performance, and keep fuel costs down by booking in for a high-quality DPF clean.

When you book a DPF cleaning service through BookMyGarage, you get a full inspection, diagnosis and flush, all performed by highly-qualified mechanics, for as little as £99!

Reduce your carbon footprint and save on unexpected replacement DPF costs today!