Yes, that's right... 50% coolant and 50% water... distilled water preferred.
Nowdays, they are selling premixed coolant because they handled the water in
different way... easy to use and cost about the same... meaning 1 bottle of
pure coolant = 2 bottles of premixed (slightly more $).
In US, Zerex G-05 is what MB use... but on some newer MB car, I am seeing
green coolant... so see what you have... they are both interchangeble... I
prefer the Amber colored G-05 over anything else... in personal experience,