'FS' will be to create a different brand name to the existing, approved, brand name on the OEM approval lists.
The meaning can be whatever you want it to be - its largely unimportant - if it was then it would have been written on the product, in this scenario its purpose is to differentiate the product from Mobil 1 0W-40 product which has BMW approval and is on the BMW global approved list.
The meaning can be whatever you want it to be - its largely unimportant - if it was then it would have been written on the product, in this scenario its purpose is to differentiate the product from Mobil 1 0W-40 product which has BMW approval and is on the BMW global approved list.