Does anyone know the optimum cetane requirement for the 3.0TDI engine. I have read numerous articles which indicate it may be detrimental to run an engine on a lower than recommended cetane level (rough operation, low power output, excessive deposits, wear and hard starting). My goal is to use a fuel that will yield the best mileage at the lowest life cycle cost for 250K miles. Unfortunately the 2012 Touareg owners manual does not indicate the minimum cetane level. Instead, it says that ULSD should meet ASTM D975 specification. FYI: A higher cetane number means a shorter ignition delay time and more complete combustion of the fuel charge in the combustion chamber. This, of course, translates into a smoother running, better performing engine with more power and fewer harmful emissions. Additional information I have read says that using a higher cetane number fuel will yield no better results than one would experience with a gasoline engine when using 89 or 92 octane fuel in an engine designed to run on 87 octane fuel.