The Importance of Maintaining your Diesel Particulate Filters

If you are the owner of a diesel car, your vehicle will no doubt be fitted with a diesel particulate filter (DPF) which have been fitted to diesel cars for over 20 years.  What many diesel owners don’t know is that it is important to maintain this vehicle part to avoid expensive repairs or replacement parts in the future.

So, what can you do to look after your DPF for maximum performance and to minimise wear and tear? The team at FMP Motor Factors has come up with these guidelines:

A diesel particulate filter explained

A DPF is a filter that captures and stores exhaust soot in order to reduce emissions from diesel cars. But because they only have a finite capacity, this trapped soot periodically has to be emptied or ‘burned off’ to regenerate the DPF.

This regeneration process cleanly burns off the excess soot deposited in the filter, reducing the harmful exhaust emission and helps to prevent the tell-tale black smoke you used to see from diesel vehicles, particularly when accelerating.

Euro 5 exhaust emissions legislation introduced in 2009 to help lower car CO2 emissions effectively made DPFs mandatory, and since then, around one in two new cars a year have been diesel-powered.

If the owner of a diesel vehicle removes the DPF from the vehicle, they could face fines of up to £1,000 for cars and £2,500 for vans as well as invalidating your car insurance policy.

Warning Signs of DPF blockages

If your DPF is becoming clogged with soot or a fault develops in the system, an orange light will typically appear on the dashboard.

Short journeys at low speeds are the prime cause of blocked diesel particulate filters. This is why car makers often recommend that city-bound short-hop drivers choose a petrol car instead of diesel.

Poor servicing is another reason why DPF’s can stop being effective. A diesel particulate filter on a poorly serviced car may fail sooner than a well maintained one. It’s also important to use the right type of oil as some oils contain additives that can actually block filters.

In addition, performance modifications can damage a diesel particulate filter, as can using low-quality fuel and even running the car frequently on a low fuel level as the car may avoid DPF regeneration in order to save fuel.

Maintaining a DPF

The best way to maintain a DPF is to make sure it’s fully able to regenerate itself when it’s full of soot (ie when the warning light appears).

There are two types of regeneration: passive and active.

  • Passive regeneration which occurs when the car is running at speed on long motorway journeys, allowing the exhaust temperature to increase to a higher level and cleanly burn off the excess soot in the filter. It is advised that drivers regularly give their diesel vehicle a good 30 to 50 minute run at sustained speed on a motorway or A-road to help clear the filter.
  • Active regeneration means extra fuel is injected automatically, as part of the vehicle’s ECU, when a filter reaches a predetermined limit (normally about 45%) to raise the temperature of the exhaust and burn off the stored soot. But problems can occur if the journey is too short, as the regeneration process may not complete fully. If this is the case the warning light will continue to show the filter is still partially blocked. A driver should then complete a regeneration cycle and clear the warning light by driving for 10 minutes or so at speeds greater than 40mph.

Signs that active regeneration is taking place include:

  • Engine note change
  • Cooling fans running
  • A slight increase in fuel consumption
  • Increased idle speed
  • Deactivation of automatic Stop/Start
  • A hot, acrid smell from the exhaust

Cleaning Your DPF

To avoid having to replace your DPF when it stops functioning properly, it’s best to get the part cleaned back for improved performance and to extend its shelf-life.

Motor Factor companies such as FMP, stock the market leader in DPF cleaning systems with the Ivor Searle DPF machine.

Leading manufacturers of DPF’s have confirmed that there is no significant difference between a filter cleaned using the same technology used in the Ivor Searle product compared to installing a new one.

The benefits of getting your DPF cleaned with an Ivor Searle cleaning service include:

  • Production of ‘as new’ levels of cleanliness and back pressure
  • Low cost alternative to a new DPF
  • Removes both ash and soot
  • Environmentally friendly process
  • Industry standard guarantees.


get in touch for advice & to order your car parts


Open Mon-Fri, 8.00am - 5.30pm and Sat 8am - 1.30pm
FMP Motor Factors, Unit 1, St John's Court, Upper Fforest Way,
Swansea Enterprise Park SA6 8QQ

Port Talbot

Open Mon-Fri, 8.00am - 5.30pm and Sat 8am - 12.30pm
FMP Motor Factors, Unit 30, Baglan Industrial Park,
Port Talbot, SA12 7DJ