WHAT IS A DIESEL PARTICULATE FILTER?
Diesel particulate filters are used to reduce the exhaust emissions
as required by European legislation, especially particulate matter.
A particulate filter traps most of the soot that is produced during diesel
combustion and would normally travel down the exhaust and into the
atmosphere. These particulates can cause respiratory problems if people
are exposed to high concentrations overtime.
PARTICULATE FILTERS NEED TO “REGENERATE”
A filter can hold a certain amount of soot, but not a huge quantity, so
it needs to regularly go through a process of regeneration in order to clear
out the soot and allow the vehicle to operate properly. Regeneration occurs
when the filter reaches a sufficiently high temperature, allowing the soot
to be converted to a much smaller amount of ash. On most systems,
to allow the filter to automatically regenerate, the engine should be used
regularly at a sufficient speed, to ensure a high enough temperature of the
exhaust gas is reached.
Although it may vary from manufacturer to manufacturer, typically a
vehicle must be driven at 50mph or above for at least 20 minutes in order
to automatically regenerate the filter. During the regeneration phase, high
temperatures in the filter may cause a slight smell, especially during the
WHAT HAPPENS IF IT DOESN’T REGENERATE?
If the vehicle is not driven in a way that automatically regenerates the
particulate filter, it will build up an excessive amount of soot, which, if not
resolved, will reduce the performance of the vehicle and damage the filter.
If the filter does build up too much soot, a vehicle warning light will
appear to alert the driver. The problem can usually be resolved by
allowing the filter to automatically regenerate until the warning light
goes out – i.e. by driving the vehicle at 50mph or above for at least 20
minutes. The vehicle handbook will have specific guidance for the vehicle.
If traffic conditions and speed limits do not allow the vehicle to be driven
so that the filter regenerates, it will have to be returned to a dealer for
a forced regeneration to clear the filter. If the warning light is ignored and
the vehicle is driven without regenerating the filter, it will cause damage
to the vehicle, which will not be covered by warranty or our maintenance
agreement. We are aware of businesses in the UK who have incurred costs
in the region of £1,000 to £1,500 after a driver has failed to follow the
correct regeneration process.
SELF HEATING PARTICULATE FILTERS
The majority of vehicle manufacturers now have diesel particulate filters
that require the regeneration cycle to be driven, but not all.Some have
systems that can heat up the particulate filter and regenerate it without
the need for a higher speed drive cycle. Some inject fuel straight into the
filter which burns and therefore increases the temperature in the filter, and
others have heaters built into the filter. For specific details of individual
models, please refer to manufacturers’ websites.
ALTERNATIVES FOR URBAN DRIVERS
If drivers are restricted in their ability to regenerate a diesel particulate
filter through driving at higher speeds, there are other vehicles that can
be chosen which do not use this technology.Diesel models with the
built‐in heating systems are an option, or alternatively, a petrol, petrol
hybrid, electric or alternatively fuelled vehicle may be more suitable,
especially in urban only driving conditions.
WHICH DRIVERS SHOULD ORDER THESE VEHICLES?
Diesel particulate filters significantly reduce harmful
emissions and are vital for diesel vehicles meeting European
tailpipe emissions, but care is needed when using this
technology in predominantly urban driving conditions.
Therefore check the type of particulate filter on any diesel car
with an urban drive‐cycle and make sure it’s suitable,
otherwise consider a different fuel type or vehicle technology.