See also:

Condensation under the parked vehicle
When using the automatic climate control, condensation water develops that exits underneath the vehicle. Therefore, traces of condensed water under the vehicle are normal. ...

BMW Connected Drive
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Switch off the engine during longer stops
Switch off the engine during longer stops, e.g., at traffic lights, railroad crossings or in traffic congestion. Fuel savings are achieved after the vehicle is switched off for only approx. 4 s ...