Mystery Oil (not Marvel)
 

Greetings:

One-owner of a 2001 E55, here. I just replaced the front upper and lower control arms. If you've ever done this work, you'll know that the upper arms are a pain in the neck to get to (bolts). The passenger side is very messy, as you have to remove the ECU and other modules, etc. During that process I noticed some oil in that box and didn't think much of it. Having left the pieces out for a few days, I noticed after assembly that one of them (not actually sure which one) leaked out a good amount of oil onto the floor. It seems like it's a mineral oil, but I'm not sure.

I hope this isn't a 'doh!' moment for me... I did some searching last night on the interwebs, and I couldn't find anything on this at all. Thoughts or answers as to what this oil is, and where it came from? Thank you.