Be Particular About DPFs

Klarius explains why type-approved replacement Diesel Particulate Filters (DPFs) are essential and points to consider in order to avoid costly warranty returns.

The rise in demand for type-approved replacement DPFs is becoming more apparent as more vehicles are emerging with DPFs as standard fitment. If one is fitted at the factory, it is a legal requirement for it to be present on the vehicle in order to pass an MOT test.

As routine service items, DPFs are consistently in demand. By supplying good quality aftermarket replacements to garages, motor factors can enjoy reliable sales opportunities at a fraction of prices quoted by dealers.


Over time, a DPF fills up with soot and other particulates from the combustion process. It periodically goes through a renewal cycle where soot is burned off. Known as regeneration, the process creates a small amount of ash each time it happens, leading to the eventual blockage of the DPF’s internal ceramic monolith – requiring the component to be replaced as a service item.

The DPF is required to reach a high operating temperature before the regeneration process occurs. This is typically attained during longer journeys. If the vehicle travels mainly on short journeys, the DPF is unable to regenerate properly and can become full of soot and ash very quickly. If a forced regeneration at the garage does not successfully clear the DPF, then a replacement will be required.

This means that the need for a DPF replacement due to excess soot can vary widely, depending on the driver and vehicle. Cars with particularly dirty engines and taken on shorter journeys will create more soot, filling the DPF more often with less chances to regenerate. It is possible to need a replacement after 20,000 miles even though the replacement should usually take place between 60,000 to 80,000 miles.


Many modern diesel engines will have a DPF and catalytic converter (CAT) in order to meet the latest emissions standards. In some cases, the units are separate and can be replaced individually. However, many are combined into one part. Increasingly, the trend is to move both nearer to the exhaust manifold so that they can attain the working temperature sooner.

For example, many recent Ford models have combined the DPF and CAT into the same canister and made it part of the exhaust manifold itself. This does protect the unit more from cold water splashes and mechanical impacts, but it is more expensive to replace if engine running issues cause damage.


DPFs are relatively expensive to replace especially when they are manufactured as one component. Whilst a lower quality aftermarket replacement may look the same as a premium, type-approved unit on the outside, their stark differences in quality are more evident inside the part – even though their prices are likely to be very similar. Type Approved CATs, DPFs and combined units from Klarius typically have full-sized ceramic monoliths with a generous precious metal surface coating that makes the catalytic process work in the case of the CATs and DPFs.

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Published on: December 3, 2020

Filled Under: Exhaust, Technical Articles

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