BMW 5 series Owner's Manual page 183

Pull the green knob with the fuel pump symbol.
This releases the fuel filler flap.
Observe the following when
refueling
The fuel tank is full when the filler nozzle clicks
off the first time.
Do not overfill the fuel tank
Do not overfill the fuel tank; otherwise fuel
may escape, causing harm to the environment
and damaging the vehicle.◀
Handling fuels
Obey safety regulations posted at the gas
station.◀
Online Edition for Part no. 01 40 2 903 008 - 07 12 490
Refueling Mobility
183