The volume of the tank on your A8 Saloon is 17L.
The first warning illuminates on your dashboard when the remaining AdBlue® mileage reaches 1500 miles. An alarm signal is heard to warn you. Below 650 miles, the AdBlue® warning illuminates on the dashboard. An alarm signal sounds and a message warns you that you won't be able to re-start the car once the tank is empty. As soon as the tank is empty, a message is displayed along with 3 audible alarms. To switch off the AdBlue® warning light, fill your AdBlue® tank with at least 5,7L of AdBlue®.
If your warning shows a remaining mileage of 0 miles, restarting your car is impossible once the engine has been turned off. If your engine is still running and your tank is empty, it is still possible to drive to a service station. If the car does not start after the AdBlue® top up, wait for two minutes for the system to detect it. If the AdBlue® tank is empty, turn the ignition on for about 15 seconds and then start the engine.
This information can vary on some vehicles of the same model in relation to the options chosen by the manufacturer.