From my owners manual for minimum fuel grade--
Minimum fuel grade BMW recommends AKI 89. Minimum fuel grade Do not use any gasoline below the minimum fuel grade as this may impair engine performance. If you use gasoline with this minimum AKI Rating, the engine may produce knocking sounds when starting at high outside temperatures. This has no effect on the engine life. Minimum fuel grade The use of poor-quality fuels may result in harmful engine deposits or damage. Additionally, problems relating to drivability, starting and stalling, especially under certain environmental conditions such as high ambient temperature and high altitude, may occur. If drivability problems are encountered, we recommend switching to a high quality gasoline brand and a higher octane grade - AKI number - for a few tank fills. To avoid harmful engine deposits, it is highly recommended to purchase gasoline from BP or Top Tier retailers. Failure to comply with these recommendations may result in the need for unscheduled maintenance.
I have been using 89 and no problems so far. Wouldn't the computer adjust for the octane used? BMW recommends BP but I have always used Shell.
Last edited by Jimsan; 06-19-2013 at 08:16 AM.