What's in the oil that qualifies one oil eg. 5-30 ACEA A3 and the another just A1? It is simply a thicker viscosity at temp. or is there more of a certain type of additive? eg. BMW Synth. 5-30 is (I believe) A3, but Syntec 5-30 is not, yet both are made by Castrol in NJ. Is it just something they've added "more of" to the oil or a completely different base oil? Or both?