BMW 5 Series: Remove attached parts 
following use - Saving fuel - Driving tips - BMW 5 Series Owners ManualsBMW 5 Series: Remove attached parts following use

Remove auxiliary mirrors, roof or rear luggage racks which are no longer required following use.

Attached parts on the vehicle impair the aerodynamics and increase the fuel consumption.

    Remove unnecessary cargo
    Additional weight increases fuel consumption. ...

    Close the windows and glass sunroof
    Driving with the glass sunroof and windows open results in increased air resistance and raises fuel consumption. ...

    See also:

    Wheels
    If a wheel is bent, cracked or heavily corroded, it should be replaced. Otherwise, the tire may separate from the wheel or cause a loss of handling control. ...

    Recommended clutch fluid
    CAUTION Never use different brands of clutch fluid together. Also, avoid mixing DOT 3 and DOT 4 brake fluids even if they are the same brand. ...

    Washer fluid
    Checking the washer fluid level The reservoir is translucent so that you can check the level with a quick visual inspection. Check the fluid level in the washer fluid reservoir and add fluid if ...