I searched this online and am seeing the option of numerous types viscosity of oil, which I thought is odd. Just purchased a 2021 C300 for my wife, and I do the oil changes. I am seeing 0-20, 5-30, 5-40 for use in the vehicle? Can someone clarify this for me please? Can I really use all of these?? Also, did a search for oil capacity and found 6.3 quarts....then I am seeing 7 quarts for 2 wheel drive & 6.3 quarts for the C300 4matic. Is this correct?

Much thanks!!