A blocked DPF (Diesel Particulate Filter) can cause serious engine issues, reducing power and increasing fuel consumption. 

Common symptoms include the DPF warning light, loss of power, black smoke, and poor fuel economy. This guide explains the signs of a clogged DPF and how to fix it.

Key Takeaways

What is a DPF?

A DPF filter captures harmful soot particles from diesel exhaust, holding them until they can be burned into less harmful ash through a high-temperature regeneration process.

Fun Fact: Since 2009, DPFs have been mandatory on diesel cars.

8 symptoms of blocked DPF

A blocked Diesel Particulate Filter (DPF) is a common issue in diesel vehicles, with the flashing orange DPF warning light being the most obvious sign. 

But there are other symptoms to watch for, such as:

DPF Warning Light on the Dashboard

The most obvious sign of a blocked DPF is the illuminated warning light on your dashboard. This indicates that the filter is clogged and may need to be regenerated or cleaned.

Loss of Engine Power & Sluggish Acceleration

If your engine feels sluggish and lacks the usual power, it could be due to a blocked DPF. This restriction can limit the engine's efficiency and performance, causing a noticeable loss of power.

Inability to Rev Past a Certain RPM

A blocked DPF can prevent your engine from revving past a certain RPM. This is because the engine’s exhaust gases can’t flow freely, which can cause the vehicle to feel restricted.

Black Smoke from the Exhaust

When the DPF is clogged, incomplete combustion of fuel can cause black smoke to be emitted from the exhaust. This is an indication that the engine is struggling to properly filter exhaust gases.

Difficulty Starting the Engine

A clogged DPF can lead to starting issues, especially if the filter is severely blocked. If your vehicle struggles to start, it could be related to poor exhaust flow due to the blocked filter.

Reduced fuel economy

When the DPF is not functioning optimally, your vehicle may burn more fuel than usual, resulting in reduced fuel efficiency. This happens because the engine works harder to push exhaust gases through the clogged filter.

Start-stop function not working

In many modern vehicles, the start-stop function helps save fuel by turning off the engine when idling. 

A blocked DPF can cause this function to stop working, as the engine may need to stay running to maintain exhaust flow.

Strong diesel smell inside the cabin

A strong smell of diesel inside the cabin could indicate that the DPF is not properly filtering the exhaust gases. This can result in unburned fuel entering the cabin, which can be harmful to both the driver and passengers.

Quick fixes for a blocked DPF

Noticed some clogged DPF symptoms? Here are a few quick fixes for each problem.

If any of the issues above persist, a professional DPF clean may be necessary to restore optimal performance and prevent further damage to your vehicle.

Can I fix a blocked DPF myself?

You can use DIY techniques to tend to minor DPF problems. These basic fixes include driving at a higher speed and using a DPF cleaning additive.

While these can help clear blocked DPF symptoms, it’s best to consult a professional for thorough cleaning in case the blockage is significant. In a few cases, you may need a replacement, which is always best done by a professional.

What happens if you ignore a blocked DPF?

Ignoring a blocked DPF can lead to poor engine performance, increased fuel consumption, and potentially severe engine or exhaust system damage. 

These can even lead to costly repairs and reduced vehicle lifespan. Not ideal! If you think your diesel particulate filter is clogged, get it checked out as soon as possible. 

How to avoid a clogged DPF 

Luckily, you can avoid a clogged DPF. Here are the top 3 tips drivers need to know to ensure their diesel particulate filter isn’t clogged.

1. Don’t only drive short distances

Sadly, diesel cars aren’t great if you only want to pop to and from the shops.  

The exhaust needs to be hot to burn off the soot. If it never reaches a temperature high enough, it will only become more blocked.  

To mitigate this, ensure at least once a week it makes a journey above 40mph for over 30 minutes, or more if possible. This is your sign to hit the motorway!

2. Use the correct oil

Special oils have been developed for use in DPF-fitted cars. These have lower element content to avoid soot buildup (e.g. Sulphated Ash, Phosphorus and Sulphur). 

You'll find these labelled low SAPS at any regular shop selling engine oil. For more information about oils, find out how often you should change your oil in our handy guide.

3. Take care of any other engine issues promptly

Diesels are generally more complex than petrol engines. They have more components that can fail and cause issues with DPFs.  

You should pay close attention to any issues on:

• Stuck or faulty injectors
• Failing turbo seals
• EGR valve issues

The above can cause excess oil or soot to exit the engine through miss-fueling or oil consumption. These will clog up a DPF in record time, so be on the lookout for dash warning lights and act quickly.

How long does a DPF last before it needs replacing? 

A DPF typically lasts between 80,000 to 150,000 miles. This can depend on your driving habits and vehicle maintenance. 

Regular long drives help extend its lifespan, while lots of stop-start city driving may cause it to wear out sooner. 

Average DPF replacement costs

A DPF replacement costs between £800 to £2,000.

DPF replacement costs are affected by the vehicle's make and model, the type of DPF required, labour costs, and whether the DPF is an aftermarket or original part.

Some garages specialise in replacement DPFs, but generally, most normal garages can remove and replace a DPF. 

How long does a DPF last?

With proper maintenance and regular longer journeys, a DPF can last up to 100,000 miles. So, don’t delay those road trips—frequent driving helps keep the DPF functioning well.

Is it illegal to remove a DPF?

Yes, it’s illegal, and you’ll face an invalidated insurance policy and a fine (up to £1,000 for cars and around £2,500 for vans). 

Even if your diesel particulate filter is clogged, you should never remove it.

The takeaway

Think your DPF is clogged? Hopefully, this blog has helped you understand DPF clogs, the symptoms, and how to prevent this problem. While you hopefully won't face this pesky issue, knowing how to navigate it will help you save time if it happens.

Split the cost with Bumper 

If you need to fix your DPF and are worried about costs, Bumper is here to help.

With Bumper's car repair finance, you can split the cost of DPF replacements and other repairs into monthly instalments, completely interest-free.

Choose from thousands of trusted and reliable repairers.