I bought my '04 545i second hand. According to the owner, it had all original everything at 180,000 kms!
The transmission had a leak and was serviced by BMW at 100,000 kms - including oil replacement.

Anywhoos, I replaced the diff oil at 180k and was amazed at how clean it looked. It was still, generally a honey like colour, but had a definite 'burnt gear oil' smell.
Very few fine flakes at the bottom of the drain pan as well. Sorry, didn't take pics.
I was certainly surprised at the results of the original oil.
I supported the stealer here and purchased BMW lifetime oil at $42 per liter!!!
I know.....I know....but it proved itself in the first 180k.
I like the mag drain plug idea as well - next time.

Thought I would share some long term oil results anyway.

so which should i use for my 550i?

I'm with BMW on the differential oil being lifetime. This is from Experience.

Just changed my oil today with 101k miles. It was a light brown/honey color just slightly darker than the redline fluid. I'll probably change it out again to OEM fluid in a few months. My dealership charged me about $8 for the plug tho.

Thanks for the info, guys!

According to Realoem.com, the recommended fluid for my 2006 BMW 530i (VIN CM30564) is Final-drive gear oil SAF-XO (part 33117695240). I am also looking at the BMW Genuine OEM Synthetic gear oil SAF-XO (Part #07-51-2-293-972). Could someone please confirm whether I can use either one?

http://realoem.com/bmw/diagrams/w/k/553.png

Thanks! :-)

did you guys notice any vast difference in the driving experience after changing this fluid by any chance

'08 E60 550i is this the only type of differential they came as stock from factory?
What type of BMW oil to use?

http://i64.tinypic.com/2h6t821.jpg