best-selling is also not relevant to what 'works.' as you say, "most drivers dont judge by recipy,they dont bother to know."
and since you are replying to me, it's important to note you were the one that brought up Quaker State and motul. I was comparing Mobil 1 Full Synthetic 5w40 to 0w40 FS. In which case I do not believe there is any serious debate, except in the "which oil boils more on the stove" test. 0w40 FS is the clear flagship product for Mobil 1 Euro full saps oils. if you're going by 'most good selling' then that would also be 0w40 FS based on the online marketplace here.