As the market for biodiesel grows, so too does the availability of this fuel. In Germany around 1,900 filling stations offered biodiesel in 2007. However, any driver interested in using this “green fuel” should pay attention to a few points. First, of course, his or her car must be suitable, a condition currently met by a great number of diesel vehicles. But biodiesel shouldn’t be used unless expressly permitted by the car manufacturer, otherwise the vehicle warranty could be affected. If in doubt, the car owner should look in the instruction manual or ask the manfacturer.  The "Arbeitsgemeinschaft Qualitätsmanagement Biodiesel" (Biodiesel Quality Management Association) - AGQM -  monitors which oils are used, and issues a quality seal. Drivers should always keep a look out for this seal when they fill up. The German automobile club ADAC has compiled a list of vehicles that are capable of running on biodiesel. Furthermore, the "Union zur Förderung von Oel- und Proteinpflanzen" (Union for Promoting Oil and Protein Plants) maintains a directory of biodiesel filling stations bearing the AGQM quality seal.