In partnership with French authorities, official laboratories and transport companies, ONIDOL, the French Oilcrop, Association, has managed an experimental programme on the use of Rapeseed Oil Methyl Ester (RME) as diesel fuel. For three years, 30 % - 70 % blends of RNM and diesel fuel, 50 % - 50 % blends and pure ester have been tested on regular bus services as well as on fleets of trucks and light vehicles. At present, in about 60 French cities, some 2,000 vehicles are using 30 % RME and more. Such a large-scale program has given extremely accurate information, leading to nation-wide use.Three fleets have been following a stricter control of lubricating oil and engine deposits with reference vehicles performing the same service on diesel fuel. Chassis dynamometer tests have also enabled a more precise comparison of performance and emissions to be obtained.Fuel consumption, emissions, cold performance, long-term behavior of engine parts and lubricating oil are compared. The use of the 30 % - 70 % blend gives the same efficiency, reduces hydrocarbons, aromatics and particles without a noticeable effect on nitrogen oxide emissions. For a more than 30 % RME blend, although reduction in lubricant viscosity has been observed, effects on engine wear and cleanness were surprisingly as good as reference diesel fuel or even better. These experiments have contributed to technically validate the increasing use in blends of RME produced in accordance with French specifications.