We all know that Mobil 1 0w40 meets all the toughest European OEM extended drain specs, but what is about the oil that enables it to meet those specs? Looking at the VOAs of all the grades of Mobil 1, the only real difference as far as additives is the 0w40 has more calcium. And except for the 15w50, the 0w40 would have a higher HT/HS, giving it the A3 rating. But is that it? Is it the higher HT/HS vis that gives the 0w40 the "edge" when it comes to the tough European OEM requirements?