This is a photo of the tranfer case oil I drained from my 99 ML 320 with 95K miles. It's black but has no metal shavings in it and no mettalic look to it at all.

Questions:

1-Isn't this oil kind of dirty? Although that may have been the color when it was new.
2-If it is dirty does it affect it's performance with respect to the life of the transfer case?

Mercedes says it never needs to be changed. Is that because:
1-They are telling the truth?
2-They want us to think that our vehicles don't require maintance for certain components and use that pitch to sell the vehicles?
3-They want to sell transfer cases and have customers incurr service charges to replace tranfer cases because they wear out from lack of any maintainance?