What brand of ATF in the steering system is not as important as how old it is in there. Here is how I change out mine annually:

1. Siphon out the old fluid from the reservoir
2. Fill with new fluid
3. Turn the steering wheel from side to side a few time
4. Repeat 1-3 for 2 more times

Alex, I've never heard of a mb4 engine in a E53. It's M54B30.

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00 E39 DINAN S1 //M5 (82k miles)
06 E53 DINAN 4.8iS, born 2/18/2006 (126k miles) http://www.xoutpost.com/bmw-sav-foru...s-my-dslr.html
90 Straman Z32 TwinTurbo Convertible, (1 of 44 ever made) 5 speed, 444rwhp/451rwtq
01 360 Novitec Spider F1 (26k miles)