The volume of the tank on your E-class Saloon W212 is 8,5L or 24,5L.
In case the level of AdBlue® drops to the reserve level of 3.0L, which corresponds to a mileage of 1500 miles, the message “Add AdBlue® see instruction manual" will appear on the multifunction display. Then message "top-up AdBlue® mileage: ...km" is displayed on the dial switch indicating to you your remaining mileage. Following the process of filling up, if you drive a speed faster than 10 miles/hour, the warning message will go off after a delay of around one minute. If the event of a completely empty tank, pour a minimum of 3,5 L to switch the warning off.
As soon as your tank is empty and that you turn the engine off, you cannot restart the car. If the engine is still running, you are able to drive to a service station. After the fill up, turn the ignition on for 60 minutes and start the engine.
This information can vary on some vehicles of the same model in relation to the options chosen by the manufacturer.