Active Regeneration

Active regeneration of the DPF is performed by the ECU triggering a post combustion fuel injection. This increases the temperature in the DPF, burning off the soot and particles that build up in the filter. This type of regeneration can cause higher than normal fuel usage.


Passive Regeneration

Passive DPF regeneration takes place automatically on motorway-type runs when the exhaust temperature is high. Many manufacturers have moved to using active regeneration as many motorists do not often drive prolonged distances at motorway speeds. Passive regeneration often uses a DPF additive.


What is a DPF additive?

DPF cleaning additives are a chemical solution added to the fuel tank which claims to aid the cleaning of a DPF filter. Some manufactures utilise a DPF additive which is automatically added to the fuel which is used to increase the chance of a passive regeneration. The additive allows the soot and ash to be “burnt” at a much lower temperature than that required during an active regeneration. The additive is usually replenished during servicing as part of manufactures guidelines. The additive contains a “Fuel Borne Catalyst” which in most cases is cerium oxide. This catalyst does not help increase the temperature of the DPF during a cleaning cycle however it does work to decrease the temperature at which the soot blocking the DPF will “burn off”.


Do DPF cleaning additives work?

NO. Fuel additives have been attributed with reducing emissions and soot from the fuel burning process which could reduce the chance of the DPF being blocked. Claims that an additive can unblock the DPF and extinguish the warning light are simply untrue. By the time the additive has been through the combustion process there will be very little left and certainly won’t be capable of unblocking the DPF.


Forced Regeneration

Forced regeneration is a way of cleaning the DPF using a maintenance process which has been built in by the vehicle manufacturer. This process can only be started by either a main dealer / mechanic with the right tools and access to the vehicles management systems. This process usually involves kicking off a DPF clean cycle in the workshop which runs the car at a high RPM for a considerable period of time. The ECU ensures that this cycle heats up the DPF filter to an extreme temperature, burning off the contents of the filter. It some cases the ECU injects fuel into the post combustion process to achieve these temperatures. In most cases the engine oil will need to be changed as the vehicle will literally “cook” the lubricant.


Can I remove my DPF?

Due to the high costs of replacing diesel particulate filters, a whole industry has emerged around removing the devices completely (DPF removal). This involves replacing the unit with a pass through pipe or modifying the existing unit and removing the mesh or filters inside.

The removal of the DPF will cause an ECU error and therefore the service will  also include the removal of the error and re- programming from the ECU software.

The marketing of these services often includes claims of reduced running costs, extra power and increased efficiency. Recent evidence shows when a Diesel Particulate Filter has been removed, rather than cleaned or replaced, the back pressure of which the turbo relies on is altered. This results in the turbo charger performance being seriously affected which will lead to its inevitable early failure, and another very costly issue to deal with.