Peeps,,,its the type of car and the recomended fuel type..simple as that.
ADNOC caters to all segments of users. Eplus is cheaper and there are many takers for the same for that particular types of cars that accept. Nothing wrong with the fuel. I use Eplus for my Pajero for the past 7 years and I have had no issues, and I read through the manuals and it falls in that category of OCTANE count and so it was fine.
Since it is not recommended for german cars, I use Special for the mercedes.
Next time if you are not sure of the fuel type... I guess, call up some Emergency services and they will bring the fuel.