There is a drilling in the side of the plug in which you can put a size 3 Allen key or a Torx key T10 (usually found in the your BMW toolkit) in order to fit and remove it.
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Also referred to as oil filler cap.
A better view of the rear wheel is possible thanks to the...
These covers for the open holes of the engine mounting are...
After just a few thousand kilometers, stones and dirt thrown...