Originally Posted by BMWM.D.
Alright, I have an answer to our questions. The "special" oil (83 22 2 282 583) is described on the bottle as "SAF-XJ + FM Booster". So, it is the same oil with the addition of some type of extra friction modifier or "booster".
I put in a quick call to Castrol technical support and their answer was that they produce SAF-XJ with friction modifiers to BMW...if BMW then mix in further additives and repackage it with their own part number then its nothing to do with Castrol.