I have had my S3 now for just over a year (wow, that has flown!) and the coolant level was on the minimum line of the expansion tank so I put in some more Audi stuff (ffs, how much?)
I cannot see any leaks, so over time where is this going? LOL. Even though it is supposedly a sealed system and the additives change the boiling point, etc, does it still evaporate?
Now don't get me wrong, having a car thats done 12k miles over a year and only having to fill up from min to max does not worry me, it is more of a "where the hell does it go?" type question.