What is the capacity of AdBlue?

[WanderlustGuru]

My 2014 C220 D has indicated that I need to replenish the AdBlue.

My independent repair technician advised me to add 10 litres, which I have done, and the notice has now disappeared.

I purchased an additional 10 litres, since internet sources said that the tank had a capacity of 25 litres.
Costco offers an excellent pricing of around £12 for 10 litres.

What is the remaining fuel level when the warning message appears?
My vehicle lacks the capability to monitor the AdBlue level on the dashboard.
I want to avoid overfilling and then dealing with AdBlue spillage that requires extensive cleanup.

Assistance would be appreciated.

[BENZE220AMG]

Does the guide not include the figure?

[motorman3]

Neglecting to replenish the tank causes AdBlue to deplete and crystallise. It is advisable to maintain a few litres of fuel to avoid incurring substantial costs when the engine indicates it will not start within 500 miles.

[BENZE220AMG]

However, it is not quite clear-cut according to this

[BENZE220AMG]

https://www.tuffa.co.uk/how-to-avoid-adblue-crystallisation/

[motorman3]

Their recommendation is to maintain a full tank; however, it has never been effective for me.
It seems that the whole piece was authored by AI; however, it was really composed by Tuffa Tanks, a company that sells storage tanks for commercial AdBlue applications.
The best laugh is this advice,

To ensure the functionality of AdBlue and prevent crystallisation, it is essential to maintain its pump and pipeline by cleaning these components when the ignition is switched off. Thoroughly emptying the pipeline is the foremost method to avert any issues, including crystallisation.

We recommend establishing a routine for cleaning the pump as often as necessary; your future self will appreciate it, and it will optimise the use of your AdBlue product by significantly reducing waste.

[WanderlustGuru]

Thank you, everyone.

The text states that "you keep the tank full," however @BENZE220AMG advocates for the contrary.
I was unaware of the complexities associated with using AdBlue.

[BENZE220AMG]

Upon spending £2000 to £3000 in repairs, you will begin to comprehend.

[WanderlustGuru]

There is no need for the hostility. I do not question your expertise.
I was unaware of the concerns, which is why I am asking these questions first.

I have had the vehicle for little more than two years, have driven around 20,000 miles, and have maintained it meticulously; this is the first time it has requested AdBlue.

[nickoyster4]

It is not an attitude; he is only expressing honesty.

MB's AdBlue system is often malfunctioning, costly to troubleshoot, and often irreparable.

In the event of a failure of the AdBlue level sensor, your vehicle will cease operation. Upon transport to the dealership via a low loader, you will be informed that the AdBlue level sensor is only available as part of the complete AdBlue tank, which costs over a thousand dollars for the component alone. Additionally, inexplicably, there are costly NOx sensors that must also be replaced concurrently, along with various other components of the AdBlue system.

£3,000 to £6,000 is not implausible. It is a subpar system. I apologise for the reaction, but rf065 was only being honest.