So I was checking my oil level through on my dash and I noticed I was a little low on oil (In between low and full level). So when I got home I decided to top it off. But after I twisted off the oil cap I noticed that there was yellow/white gunk. This is the first time i've ever seen this. This is not coolant is it??? I have an extended warranty thru BMW. Do you think i should bring this in? Is this normal?