In light of the recent scandal revolving around the VW diesel #emissionsgate, diesel cars are firmly in the spot light for all the wrong reasons. Sure, diesel cars use less fuel, save us money at the pumps and offer comparatively more torque than their petrol cousins but what many people fail to think about is the dreaded DPF filter.

DPF filters are ceramic and fine mesh filters which clean diesel exhaust gases of nasty particulates and soot. They are a vital part of any modern diesel engines but can very quickly wipe out any benefits of diesel car ownership.

We’ve done a lot of articles around how DPF filters work and how they are cleaned but very little on the main causes of DPF diesel particulate filter issues, so here are our top 5 causes of DPF issues.

Faulty EGR

EGR (exhaust gas return) valves are designed to reduce nasty emissions by recirculating waste exhaust gases back into a diesel engine. They are vital in reducing nitrous oxide (NOx) emissions however when they do wrong they can cause all manner of issues.

EGR valves reduce the available oxygen in the cylinder, this in turn increases the production of diesel particulates (fuel which has only partially combusted). A faulty EGR valve will increase the amount of particulates produced by the engine, causing your DPF to become blocked quicker than usual.

Find out more in our EGR Valve Frequent asked questions page


Using the Wrong Oil

Most vehicles manufacturers specify a low SAPS / Ash oil. Low SAPS oils are specifically designed to be low in Sulphated Ash – a by-product of diesel combustion that causes the DPF “mesh” filter to become prematurely blocked. If in doubt we suggest that your oil changes with the recommended oil type for your vehicle. An oil change is much cheaper than a DPF regeneration… trust us!

If you’re looking for low SAPs oil and are handy with the spanners then why not change the oil yourself. Amazon has a great selection of engine oils at prices to make your local grease monkey blush

Faulty / Failed fuel Injectors

Until recently faulty fuel injectors have been a topic that’s flown under the radar when looking at causes of blocked DPF filters. We were contacted by a frustrated motorist who experienced issues with his DPF blocking on a regular basis. The root cause was finally diagnosed as a faulty fuel injector providing too much diesel fuel into the delicate air / fuel mixture. This excess fuel caused the car to run rich with the resulting excess soot clogging up the filter.

Faulty Turbo charger

A faulty turbo charger can cause havoc for a modern diesel powered car. Anything to upset the delicate air fuel mixture causing your diesel engine to belch out even more of the nasty black soot than it already does. A faulty turbo charger may also leak oil huge quantities of oil into the fuel system resulting the DPF being drowned in a sea of engine oil.

Short journeys

The start stop nature of urban driving is one of the biggest reasons many drivers experience blockage issues. Short journeys, low speeds and the start stop nature of driving built up areas can make it near impossible to replicate the conditions needed for an active or passive DPF regeneration.

Let’s hear from you!

If you’ve been one of the many motorists effected by DPF failures and blockages we’d love to hear from you, please leave a comment below or get in touch via out contact page.

Read more on DPFs below: