BMW 525tds Touring (E39), biodiesel

A Touring model was launched in the marketplace in 1997 at the same time as the sedan. This was modified so it was suitable for running on biodiesel. All the seals and fuel hoses were made of fluororubber so that the vehicle could run on rapeseed methyl ester (RME) and the tank was also modified. The customer made a supplementary payment of DM 350 for these upgrade measures. As well as offering tax benefits (exemption from fuel duty for mineral oil), running on biodiesel offered the environmental advantage of reducing emission levels of carbon monoxide, hydrocarbons, particles and soot. However, this benefit contrasted with a slightly increased emission of nitrogen oxides (NOx).