Changes to new car emissions legislation scheduled for 2009; the 'Euro 5' standards, will make particulate filters as trivial in diesel car exhausts as catalytic converters are on petrol automobiles.
Certainly, changes to fashions that were driving could be required from these emission-reducing systems for maximum advantage.
How do the filters work?:
Diesel Particulate filters (DPF) or 'snares' do just that, they catch bits of soot in the exhaust.
For a DPF this process is known as 'regeneration'; the collected soot is burnt off at high temperature to leave only a miniature ash deposit. Regeneration could be either active or passive.
Passive regeneration
Passive regeneration takes place automatically on motorway-sort runs when the exhaust temperature is high. Many cars don't get this kind of use though so makers have to design-in 'energetic' regeneration where the engine management computer (ECU) takes control of the process.
Lively regeneration
If the journey's a bit stop/start the regeneration may not finish along with the warning light will illuminate to show the DPF is partially blocked.
It should be possible to begin a regeneration that is complete and clear the warning light by simply driving for 10 minutes or so at speeds greater than 40mph.
If you keep driving in a comparatively slow and ignore the light, stop/start pattern when you are able to expect to see other dash warning lights illuminate also. At this stage driving at speed alone won't be adequate along with the automobile will need to visit a dealer for regeneration.
Expensive repairs:
If warnings continue to be ignored and soot loading continues to increase then the most likely outcome will be a new DPF costing around GBP1000.
Largely town based driving:
If lease car use or your own car use is primarily town-established, stop/start driving it would be a good idea to choose petrol rather than risk the hassle of incomplete DPF regeneration.
DPF additives:
The most typical type of DPF is found very close to the engine so that passive regeneration is possible, where exhaust gases will be comparatively hot and features an incorporated oxidising catalytic converter.
There is not always space close to the engine though so some manufacturers utilize an alternate form of DPF which relies on a fuel additive to reduce the ignition temperature of the soot particles in order that the DPF may be found further from the engine.
The additive is kept in another tank and is mechanically blended with the fuel when you fill up. Tiny quantities are required though a litre of additive should treat around 2800 litres of fuel.
You shouldn't notice anything other than maybe a puff of white smoke from the exhaust when the procedure is completed.
AA encounter:
The AA has seen evidence of DPF systems neglecting to regenerate - even on cars - which are used mainly on motorways. Their decision is that on cars with a very high sixth gear engine revs are too low to produce sufficient exhaust temperature, but occasional tougher driving in lower gears ought to be enough to dpf filter removal bum off the soot in such cases.
Examine the handbook:
Should you buy or rent a car with a DPF matched it's important to read the applicable section of the automobile handbook so you realize precisely what actions to take if the warning light illuminates and how, if at all, your driving style may need to be adjusted to ensure maximum DPF efficiency and life.
