Diesel Particulate Filter
Following changes to new car emissions legislation in 2009, 'Euro 5' emission standards have made particulate filters as commonplace in diesel car exhaust systems as catalytic converters are on petrol cars.
The goal was an 80% reduction in diesel particulate (soot) emissions, but the technology does have potential problems; roadside assistance patrols are already being called to cars with the particulate filter warning light illuminated, which normally indicates a partial blockage of the DPF filter.
Clearly, changes to driving styles may be required for maximum benefit from these emission-reducing systems.
How do the filters work?
Diesel Particulate filters (DPF) or 'traps' do just that, they catch bits of soot in the exhaust.
As with any filter (think of the bag in your vacuum cleaner) they have to be emptied regularly to maintain performance. For a DPF this process is called 'regeneration'; the accumulated soot is burnt off at high temperature to leave only a tiny ash residue. Regeneration may be either passive or active.
Passive regeneration takes place automatically on motorway-type runs when the exhaust temperature is high. Many cars don't get this sort of use though so manufacturers have to design-in 'active' regeneration where the engine management computer (ECU) takes control of the process.
When the soot loading in the filter reaches a set limit (about 45%) the ECU can make small adjustments to the fuel injection timing to increase the exhaust temperature and initiate regeneration. If the journey's a bit stop/start the regeneration may not complete and the warning light will illuminate to show that the DPF is partially blocked.
It should be possible to start a complete regeneration and clear the warning light simply by driving for 10 minutes or so at speeds greater than 40mph.
If you ignore the light and keep driving in a relatively slow, stop/start pattern soot loading will continue to build up until around 75% when you can expect to see other dashboard warning lights illuminate too. At this point driving at speed alone will not be sufficient and the car will have to go to a dealer for regeneration.
If warnings are still ignored and soot loading continues to increase then the most likely outcome will be a new DPF costing around £1,000.
Mainly town based driving
If your own car use is mainly town-based, stop/start driving it would be wise to choose petrol rather than risk the hassle of incomplete DPF regeneration.
The most common type of DPF features an integrated oxidising catalytic converter and is located very close to the engine where exhaust gases will still be relatively hot so that passive regeneration is possible.
There's not always space close to the engine though so some manufacturers use a different type of DPF which relies on a fuel additive to lower the ignition temperature of the soot particles so that the DPF can be located further from the engine.
The additive is stored in a separate tank and is automatically mixed with the fuel whenever you fill up. Tiny quantities are required though so a litre of additive should treat around 2800 litres of fuel, enough to cover 25,000 miles at 40mpg.
With this type of DPF regeneration will be initiated by the ECU every 300 miles or so depending on vehicle use and will take 5 to 10 minutes to complete. You shouldn't notice anything other than perhaps a puff of white smoke from the exhaust when the process is completed.
The AA has seen evidence of DPF systems failing to regenerate - even on cars – that are used mainly on motorways. Their conclusion is that on cars with a very high sixth gear engine revs are too low to generate sufficient exhaust temperature, but occasional harder driving in lower gears should be sufficient to burn off the soot in such cases.
Check the handbook
If you buy a car with a DPF fitted it's important to read the relevant section of the vehicle handbook so that you understand exactly 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.
ADBLUE® SOLUTION FOR DIESEL ENGINES
AdBlue® is the registered trademark for a solution that reduces emissions from the exhaust of UK diesel vehicles in order to comply with Euro 6 emissions standards. It is important that Lex Autolease customers understand the implications of choosing a vehicle requiring AdBlue® solution.
This is because it is a consumable and therefore it is the drivers responsibility to ensure that the AdBlue® solution is kept topped
up. It is also the drivers responsibility to pay all costs associated with keeping the AdBlue® solution topped up.
WHAT IS ADBLUE®?
AdBlue® is a solution made up of 32.5% high-purity urea (which comprises carbon, nitrogen, oxygen and hydrogen) and 67.5%
of de-mineralized water. The solution is colourless and is neither a fuel, or fuel additive.
HOW DOES ADBLUE® WORK?
AdBlue® solution is used in a dedicated tank in your vehicle, separate from the engine. During the Selective Catalytic Reduction
(SCR) process a chemical reaction triggered by the AdBlue® solution results in significantly reduced nitrogen oxide (NOx) emissions.
To function correctly, the AdBlue® tank of your diesel engine must be refilled with AdBlue® solution when required.
IS ADBLUE® COVERED UNDER LEX AUTOLEASE’S MAINTENANCE CONTRACT?
Lex Autolease has followed the advice of the leading manufacturers who consider AdBlue® to be a consumable similar
to fuel. We therefore deem it to be the drivers responsibility to ensure that the AdBlue® is kept topped up and to pay any costs
associated with doing so. There are one or two exceptions where certain vehicles have an AdBlue® check and top up included as
part of the scheduled servicing, so for these vehicles Lex Autolease will cover the cost of the top up during the service only.
WHEN DOES ADBLUE NEED TO BE TOPPED UP?
AdBlue® solution should last for approximately 3,500 - 13,000 miles although this will fluctuate between manufacturer's and
their model ranges. For many drivers the AdBlue solution top up can be carried out at the same time as your scheduled service, for
an additional fee. However, depending on driving style and road conditions, the maximum range of a tank of AdBlue® can vary and
therefore, the AdBlue® tank might need to be topped up in between services in a similar way to fuel, washer fluid and oil.
The average consumption of AdBlue® in UK vehicles is approximately 5% of diesel use so you will use approximately
5 litres of AdBlue® to every 100 litres of diesel. There are warning systems in the vehicle which will inform the
driver when the AdBlue® tank needs refilling. You should not ignore the warning. It is extremely important to ensure that AdBlue®
levels are adequate in order for a vehicle to continue to operate. Most vehicles will not restart if you run out of AdBlue®.
It is the drivers responsibility to ensure that the AdBlue® tank is kept topped up.
It is the drivers responsibility to pay all costs associated with keeping the AdBlue® tank topped up.
Do not ignore the AdBlue® warning light when it comes on.
Remember to refill the AdBlue® tank on time.
If the AdBlue® solution runs out the vehicle cannot be restarted after the engine has been switched off.
To enable the engine to restart, AdBlue® solution must be added.
If the wrong fluid is poured into the AdBlue® tank do not start the engine. Contact Lex Autolease immediately.
HOW IS THE ADBLUE® TOPPED UP?
Each manufacturer has a different method of topping up the AdBlue® solution and the AdBlue® tanks are located in different
places in different vehicles (e.g some are in the boot, some by the fuel filler and others under the bonnet). Manufacturers prefer to
carry out the AdBlue® tank top ups themselves, rather than drivers attempting to do this.
WHAT IS THE COST OF ADBLUE®?
The cost of AdBlue® will vary depending on the quantity purchased and which manufacturer it is purchased from.
Generally the price per litre will be higher if you decide to have a 'per litre top up' rather than a complete tank refill. Prices for
a few litres range from £5.50 upwards, but a labour charge to undertake the top up will also be applied, so the total refill cost
could be in the region of £90.00.
HOW DO I KNOW IF MY VEHICLE NEEDS ADBLUE®?
Unfortunately, it is very difficult to tell if a vehicle has AdBlue® technology by just looking at the model description. The only
way to establish if a vehicle uses AdBlue® is to check with the manufacturer.