Select: Function selector button NAV > control button Settings > Petrol station message.
When the fuel gauge is below the reserve zone, a message will appear on the MMI display when this function is on. Confirm this message, and a list of petrol stations in the immediate vicinity will be displayed. You can select one of the petrol stations using the rotary pushbutton, and the route to this station will then be calculated based on the current position of your car.