Why is my control arm leaking oil?
 

I changed the oil filter adapter and cooler gasket about a month ago. There was of course some residual oil that dropped from under the center of the car, but this just started about a week ago and I finally got a chance to crawl under and see where it is coming from. I really can't see the source, but a picture is worth a thousand words. This is on the passenger side. Crazy.

Some of the rubber bushings are supposedly oil filled and I have always wondered about that! Looks like maybe you have a leaking bushing!

My guess is your valve cover gasket is leaking and dripping on to the bushing. To my knowledge none of the suspension bushings are oil filled. The Motor mount may be. Strange looking oil though. Looks more like you spilled a coffee with cream.

Very wintery here, it is probably mixed with ice melt.

Some of them are oil filled. My e70 is up for two more new bushings only about 15 or 20k miles after the last set went in. On the e53 they hold up better but my wife just loves to hammer the brakes on the e70 (it seems to have the largest disk option available) and she got thru these quickly.

Not thrilled with that interval but I also need to change a few bushings in the LCA and refresh front diff fluid, so it'll be up off the floor for a day soon.

Your control arms look aftermarket (factory BMW are silver); I doubt the bushing is oil filled. The leak is elsewhere.

Bought it used, so am not sure they are aftermarket or not. The bushings sure look similar to the ones on my E53.
Will look at the VC this weekend and see if I can detect any leaks. I had one toward the firewall on the pass side and it was spitting oil on the rear exhaust manifold. Snugging the fasteners down a bit took care of that incident, but maybe the ones in front need the same treatment.

RealOEM.com - Online BMW Parts Catalog

Part #5 is oil filled. It needs to be replaced when it leaks on the bushing side not the balljoint side.

Yes the front Lower control arm has oil filled bushings where it mounts to the frame and a grease filled ball joint. I've replaced them myself on my older e70, it takes a good 4-5 lbs hammer to get them out.

When they leak oil its time to replace. It means your bushing has failed. It's not the end of the world but you'll get more vibration and slop in the steering.

Thrust bushing, AKA control arm AKA tension strut.

You remove the control arm, push the bushing out, new bushing in..reinstall

You should replace BOTH sides together.

If you are over 60,70k, you can replace the control arm (with bushing installed as well as ball joint) as one. You get a new ball joint that way, but an extra $160+ per side.