Diesel vehicles have had a bad rap in recent years because of the emissions they produce, having once been seen as cleaner than petrol. However, some devices help mitigate these problems.
Among them is the existence of diesel particulate filters (DPFs) on exhausts. As the RAC notes, these have been fitted as standard for nearly 20 years now.
Designed in a honeycomb pattern and made from a ceramic material, they are legally required on diesel exhausts and capture soot and ash from the exhaust that would otherwise be spewed out into the air.
The relevant legislation is the Euro 5 exhaust emissions legislation, which was incorporated into UK law in 2009. Like so much law that was drafted by the EU, it has remained on the statute books since Brexit. To abolish it would be to permit far worse air pollution.
You certainly shouldn’t remove the filter, as this is a criminal offence that can lead to a £1,000 fine for car drivers and £2,500 for van drivers. It may also invalidate your insurance policy.
DPFs are good news for the environment, given the harm that particulate matter can do, especially when it mounts up in high concentrations in urban areas with lots of traffic. Indeed, it is now an embarrassing fact for Britons who own wood-burning chimineas that these fashionable little stoves now produce more particulate matter than motorised vehicles.
Of course, this would not be so if it wasn’t for the DPF. But all the debris it collects has to go somewhere. What the device does is extract it from the exhaust so it isn’t blowing out into the air. But every so often this ash and soot will need to be burned off or emptied. This is what DPF cleaning does when other means don’t work.
Without cleaning, the capacity of the DPF would eventually be exceeded and your exhaust would be spewing lots of unpleasant black smoke. That wouldn’t just be bad for anyone breathing the nearby air; it would be a tell-tale sign that your DPF isn’t clean and you would be breaking the law.
In some cases, the DPF can be cleaned through active regeneration, which means that when the soot level reaches a certain amount of extra fuel is injected into the exhaust to burn off the excess soot and clean it out.
An alternative is passive regeneration (where the soot is burned by a hotter exhaust in a long run at high speed on a motorway). But sometimes neither method works fully, and you need to take the vehicle to the garage for a manual clean.
An orange light appearing on the dashboard can alert you to whether there is a problem. A red light will indicate that the situation is very serious and urgent attention is needed.
Having the DPF fixed and cleaned prevents a situation in which it could be damaged so badly that it needs replacing, something the RAC states could cost you between £1,000 and £3,500.
If it is looked after properly, the filter should function well for up to 100,000 miles. So if passive or active regeneration doesn’t work, don’t hesitate to come to see us and get it cleaned and looking good as new.