The volume of the tank on your X6 is 12L.
When the content of your AdBlue® tank reaches a mileage of 1500 miles, an AdBlue® warning is displayed on the dashboard. An alarm signal rings. Below 650 miles, an AdBlue® warning appears on the dashboard, along with an alarm sound and a message that warns you that restarting your car will be impossible once the tank is empty. If the tank is empty, you will be warned by a message and 3 audible alarms. Once the engine is turned off, it cannot be restarted. The warning turns itself off once you fill up.
When your tank level reaches 0 miles, you will not be able to restart the engine after it has stopped. With an empty AdBlue® tank but with a running engine, you can drive you to a service station to fill up.
This information can vary on some vehicles of the same model in relation to the options chosen by the manufacturer.