Diesel Particulate Filters (DPF) as well as the Environment
Changes to new auto emissions legislation scheduled for 2009; the 'Euro 5' standards, will make particulate filters as banal in diesel car exhausts as catalytic converters are on petrol cars.
Clearly, changes to driving fashions could be required for maximum advantage from these emission-reducing systems.
How do the filters function?:
Diesel Particulate filters (DPF) or 'traps' do just that, they get bits of soot in the exhaust.
For a DPF this procedure is known as 'regeneration'; the accumulated soot is burnt off at high temperature to leave just a tiny ash deposit. Regeneration may be either active or passive.
Passive regeneration occurs automatically on motorway-type runs when the exhaust temperature is high. Many autos don't get this sort of use though so makers have to design-in 'energetic' regeneration where the engine management computer (ECU) takes control of the process.
It ought to be possible to begin a complete regeneration and clear the warning light simply by driving for 10 minutes or so at speeds greater than 40mph.
Should you keep driving in a relatively slow and ignore the light, stop/start pattern soot loading will continue to build up until around 75% when you are able to expect to see other dashboard warning lights illuminate too. At this stage driving at speed alone will not be adequate and the automobile might have to attend a dealer for regeneration.
If warnings continue to be dismissed and soot loading continues to raise then the most likely outcome will be a new DPF costing around GBP1000.
Largely town established driving:
If your own auto use or lease car use is chiefly town-based, stop/start driving it'd be a good idea to choose petrol rather than risk the hassle of DPF regeneration that is incomplete.
The most common form of DPF is located quite close to the engine so that passive regeneration is possible where exhaust gases will still be comparatively hot and features an incorporated oxidising catalytic what is dpf in a diesel converter.
There is not consistently space near the engine though some producers use an alternative kind of DPF which relies on a fuel additive to reduce the ignition temperature of the soot particles so that the DPF can be located further from the engine.
The additive is kept in another tank and is mechanically mixed with the fuel whenever you fill up. Miniature quantities are demanded though so a litre of additive should treat around 2800 litres of fuel, enough to cover 25,000 miles at 40mpg.
With this kind of DPF regeneration will be started by the ECU every 300 miles or so depending on vehicle use and will take 5 to 10 minutes to complete. You shouldn't find anything other than perhaps a puff of white smoke from the exhaust when the procedure is completed.
The AA has seen evidence of DPF systems failing to regenerate - even on autos - that are used primarily on motorways. Their decision is the fact that on automobiles with a a sixth gear that is very high engine revs are excessively low to generate adequate exhaust temperature, but occasional more challenging driving in lower gears should be sufficient to bum off the soot in such cases.
Examine the handbook:
Should you buy or rent an automobile with a DPF fitted it is vital that you read the pertinent section of the automobile handbook in order to understand exactly what actions to take if the warning light illuminates and how, if at all, your driving style might need to be fixed to ensure maximum DPF efficiency and life.