DPF Causing You Problems? Read This Guide…

There’s recently been some press coverage over issues around ownership of new vehicles fitted with a diesel particulate filter, or DPF. It stops the nasty black smoky stuff from pouring out of the exhaust of your diesel powered car. It seems that some owners of said diesels are feeling a little mis-sold, as they are finding that their car is malfunctioning due to the DPF not regenerating. What does this mean I hear you ask?

How the DPF works
A diesel particular filter is a trap that captures ‘soot’ from the exhaust process. This is so that engines have lower emissions in order to comply with the ‘Euro 5’ standard. A diesel vehicle fitted with one is therefore better for the environment, but, depending on how you drive, it may not be better for you.

Why does it go wrong?
The diesel particulate filter can ‘regenerate’, or clean itself, but this process will not initiate if the required temperature is not reached. When the DPF temperature remains too low, the DPF can become clogged up and then performance can tail off – leading to greater emissions and potentially a drop in performance. A total lack of regeneration can also ultimately lead to DPF failure (a new DPF can cost around £1,000). Any car fitted with a DPF can be affected, not just brand new vehicles.

How can I initiate regeneration of the DPF?
The simplest way to do this is to stay in lower gears for longer and use the full rev range of your car. Perhaps ten minutes of vigorous driving should be enough to complete the regeneration process, though as with most other things mechanical this is not an exact science. Be mindful that a good motorway run in sixth gear may not be enough to regenerate the DPF if the revs remain extremely low (this will apply if you have a very tall geared car). Another suggestion is to get to speeds above 40 miles per hour and keep your car there in the power band for some minutes of driving. As always, I recommend reading your vehicle manual thoroughly for further information.

Is a diesel engined car with a DPF for me?
This question can only be answered by you. If you drive a relatively low number of miles per week and they are over very short distances, you may well be better with a small economical petrol unit or a hybrid/electric. If you still choose the diesel, you’ll have to take it for good runs to clean the DPF, which you might find a pain if that’s the only reason you’re taking the car on the journey. Alternatively, if you do a mixed run of driving and regularly give the car a run, there’s no reason why a DPF fitted diesel vehicle shouldn’t be perfect for you.

The bottom line
When you’re buying the car, check thoroughly with the seller exactly what kind of engine it has, what running requirements there are and what sort of driving style/conditions it is made for. Don’t luck out and buy something not suitable for your purposes.