Originally Posted by TrackRat
Just an FYI that the Mobil 1 0W-40 is BMW LL-01 approved and the Mobil 1 Turbo Diesel 5W-40 which is completely different chemistry is not BMW LL-01 approved and does not meet BMW warranty requirements for those who value their new vehicle warranty.
The whole concept of oil is that it's a ~20+ long carbon-hydrogen chain or cycle. There's no such thing as completely different chemistry.
(even synthetics and non synthetics only differ in purity. Their chemicals are the same ones.)
The difference between 0w40 and 5w40 TD is in additives
Such as :
Some association decides what they want in their oil, and you put it in, hand it to them, pay them (yearly), and you get a sticker.
That doesn't mean that there aren't 1000 different blends that would be as good or better.