Volkswagen has extended the engine line-up for the mid-size Passat. The saloon and estate versions are now available with a 100 kW/136 hp four-cylinder turbo diesel and the 2.0-litre TDI - first seen in the new Touran minivan and also available for the Mark V Golf - with a six-speed manual gearbox is fitted with a diesel particulate filter as standard.

The additive-assisted diesel particulate filter is located away from the engine in the vehicle underbody. Its housing is made of stainless steel and contains an innovative filter block made of silicon carbide (Si-SiC) with alternate inlet and outlet channels. The inlet channels facing the engine form a "cul-de-sac" for the soot particles. Only the exhaust gases are able to pass through the porous ceramic wall into the neighbouring outlet channel.

The retained soot particles are incinerated at approximately 500 degrees Centigrade to prevent the filter clogging and to enable it to regenerate continuously. For this purpose, an iron-based additive is put into the diesel fuel to enable the particulate matter to burn at this low temperature and to reduce ash, thus giving the filter a long service life.