2006 4.0L brown mustard looking substance in oil fill tube

[Rabid Hobbit]

I have heard that this can be a sign of a head gasket leak. Can this happen naturally. From oil seperation, condensation, using semi blend oil(Castrol) or should I be worried. BTW I just changed my oil and noticed nothing but black in the pan. Thanks in advance.
check pic please:

http://imageshack.us/photo/my-images/837/img4863z.jpg/

 

[Rabid Hobbit]

Found it out on my own. Everywhere I looked people kept saying gasket leak. But after more research (and talking to a car buff friend) this happens to alot of Ford truck owners because of the long neck of the oil tube trapping in moisture, or worse case bad PVC. Sorry if this was a dumb question but any color other than black in my oil tank worries me. Thanks

 

[swetrid]

Normal just try to clean it out.

 

[corkey]

condensation, wipe it out , go on with life,,