What You Need to Know Before Leasing a Diesel Engine Vehicle.

Diesel particulate filters (DPFs) and AdBlue diesel exhaust fluid (DEF) explained.
Both systems are designed to significantly reduce harmful emissions before they can be released into the atmosphere causing respiratory problems if people are exposed to high concentrations over time – especially in large towns and cities.

What are DPFs and DEFs?
Diesel Particulate Filters (DPF) are designed to trap soot particles produced during the combustion process whilst AdBlue Diesel Exhaust Fluid (DEF) systems are designed to reduce harmful nitrogen oxide emissions by turning them into harmless nitrogen. To achieve Euro 6 regulations (which is mandatory in order to meet London’s Ultra Low Emission Zone plans for 2020) most manufacturers are now incorporating this technology into their diesel powered vehicles.
In order to meet strict European emissions legislation, all modern diesel engine vehicles will be fitted either with a Diesel Particulate Filter (DPF) or an AdBlue Diesel Exhaust Fluid (DEF) system OR both depending on manufacturer or vehicle model.

Diesel Particulate Filters (DPF)
Diesel particulate filters need to "regenerate"
Whilst the DPF filter can hold a certain amount of soot, when it gets full it needs to clear out the soot through a process known as “regeneration”, otherwise the vehicle cannot operate properly. Regeneration occurs when the filter reaches a sufficiently high temperature, allowing the soot to be converted into a much smaller amount of ash. On most systems the engine must be driven at sufficient speed, to ensure a high enough temperature that the exhaust gas is reached.

To allow the filter to automatically regenerate typically a vehicle must be driven at 50mph or above for at least 20 minutes to effect this process.

What happens if the filter does not regenerate?
If the vehicle is not driven in a way that enables automatic regeneration, an excessive amount of soot will build up, which, if not resolved will reduce the performance of the vehicle and potentially damage the filter.
Once the filter is full, a warning light will appear on the dashboard to warn the driver. The problem can usually be resolved by allowing the filter to regenerate until the warning light goes out – i.e. by driving at 50mph or above for at least 20 minutes.
If traffic conditions or speed limits do not allow the vehicle to be driven so the filter regenerates, it will need to be taken to a franchised dealer for a forced regeneration.