2006 BMW 6 Series Owner's Manual - Page 184

Fuel specifications Never used leaded gasoline; it will permanently damage the catalytic converter.< Required fuel Controls 183 Online Edition for Part-No. 01 41 0 159 709 © 09/05 BMW AG Premium unleaded gasoline The minimum Octane Rating is 91. If you use gasoline with this minimum Octane Rating, the engine may produce knocking sounds when starting at high outside temperatures. This has no effect on the engine life. Minimum Octane Rating corresponds to the Anti Knock Index AKI and is determined according to the so-called (R+M)/2 method. Use high-quality brands Field experience has demonstrated significant differences in fuel quality: volatility, composition, additives, etc., among gasolines offered for sale in the United States and Canada. Fuels containing up to and including 10% ethanol or other oxygenates with up to 2.8% oxygen by weight, that is, 15% MTBE or 3% methanol plus an equivalent amount of co-solvent, will not void the applicable warranties with respect to defects in materials or workmanship. The use of poor-quality fuels may result in problems relating to drivability and starting, and to a tendency to stall, especially under certain environmental conditions such as high ambient temperature and high altitude. Should you encounter drivability problems, which you suspect could be related to the fuel you are using, we recommend that you respond by switching to a recognized high-quality brand. Failure to comply with these recommendations may also result in unscheduled maintenance.< Reference Mobility Communications Entertainment Navigation Driving tips At a glance