^You have a 3.0, no need to worry about an alternator bracket oil seal.

Your drain plug leaking would certainly be annoying (I had that on my 4.8i when I bought it, no crush washer was installed). Have you tried using a new crush washer? If so, maybe you could add a small amount of silicon gasket maker around the drain plug?

Honestly, if your only oil leak on a 252000 M54 is the oil drain... you're ahead of the game. Most would be leaking from the oil pan, rear main seal, and the valve cover. And even possibly the timing covers.

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2005 X5 4.4i Build 04/05 Maintenance/Build Log
Nav, Pano, Sport (Purchased 06/14 w/ 109,000 miles) (Sold 8/15 w/121,000 miles)

2006 X5 4.8is Build 11/05 Maintenance/Build Log
Nav, DSP, Pano, Running Boards, OEM Tow Hitch, Cold Weather Pckg (Purchased 08/15 w/ 90,500 miles)

2010 X5 35d Build 02/10
Nav, HiFi, 6 DVD, Sports Pckg, Cold Weather Pckg, HUD, CAS, Running Boards, Leather Dash, PDC, Pano (Purchased 03/17 w/ 136,120 miles)