No substitute as per Mike Miller schedule
Google Mike Miller BMW for the old school maintenance schedule.
There is not that much fluid in it . Somebody was saying one can from BMW is good for 2 fills . I thing the capacity is .6 liters.
Also for BMW lifetime fluid means when the cars out of warranty 100k with cpo.
As per Mike Miller old BMW schedule is pretty much like all the typical schedules for cars before free maintenance which means as little as the manufacture can get away with . (which means changing them at 30 to 60k)
Redline oil is good stuff they have and app at there website that will tell you what you can use .
Be sure to use Pentosin for the power steering fluid the type is indicated on the fill cap.
Also there are sub boards here for DIY , maintenance and a bunch of other stuff.
http://www.e90post.com/forums/forumdisplay.php?f=16