Diesel Particulate Filters

As discussed in the previous section, there are two main emissions that need to be reduced for diesels to perform well in terms of local air quality as well as global warming. Emissions of NOx which are also global warming gases 7 times more powerful than CO2, and emissions of Particulate Matter (PM). To find out more about these pollutants click here.

A EURO 4 diesel car can emit up to 0.025 grams of particulate matter per kilometre (0.04 grams per mile). However with currently available technology these emissions can be reduced to between 0.000 and 0.005 grams per kilometre.

The technology required to do this is called a Diesel Particulate Filter (DPF). A DPF can be integrated into the exhaust system where it catches the fine particles preventing them from entering the atmosphere. The systems are maintenance free and do not affect your vehicle's performance.

DPF's are beginning to emerge on the market but their application is still patchy. Peugeot have spearheaded the charge with filters being made available across a wide range of engines and models discernable by the letters FAP (French for Diesel Particulate Filter) after the model name.

If you are considering buying a diesel vehicle ask for one with a Diesel Particulate Filter, or FAP if it is from a French manufacturer. If your dealer cannot answer your questions satisfactorily (which is not uncommon at the moment) contact ECOtravel. Dealer recognition of DPF's is currently very poor, even amongst manufacturers currently fitting them, with many thinking that EURO 4 emissions standard compliance guarantees this (which it does not) or confusing DPF's with pollen filters in the car's ventilation system. If the vehicle emits more than 0.005 grams of PM per Km it does not have a filter.

The Vehicle Certification Agency publishes a list of new car emissions every May. The full emissions data are available for download from the VCA website including PM.

The EURO 5 emissions standard will be phased in between September 2009 and January 2011 with new models complying from 2009 and all models meeting the standard by 2011. In order to meet this standard emissions of PM will have to be less than 0.005 grams per Km. DPF's are the most likely candidate to meet this target meaning that by 2011 all new diesels will have one. In the meantime if the diesel that you are interested in buying does not have one, find one that does and tell your dealer why you have changed your mind!