BMW GRAN COUPE 4 Series Owner's Manual page 217

Fuel Mobility
gine deposits, it is highly recommended to
purchase gasoline from Top Tier retailers.
Failure to comply with these recommendations
may result in the need for unscheduled main‐
tenance.◀
Recommended fuel grade
BMW recommends AKI 91.
Minimum fuel grade
BMW recommends AKI 89.
If you use gasoline with this minimum AKI Rat‐
ing, the engine may produce knocking sounds
when starting at high external temperatures.
This has no effect on the engine life.
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Online Edition for Part no. 01402978272 - II/17