What is the "yucky" layer on top of my coffee?

QUESTION:

I have a fairly new, inexpensive auto-drip coffee maker. I use a common, popular brand of coffee. Whenever I make coffee, I have a greasy, dirty-like layer floating on the top of the coffee. I have cleaned the machine with a vinegar/water solution and have switched between the stainless filter and paper filters, but this still occurs. What is it? Is it safe to drink? It didn't occur with my old coffee makers.

ANSWER:

A question like this came up once before, and I'm not sure I have an answer for you.

You have cleaned your coffee maker, so we can rule out the brewer or filter as a source of the "dirty layer".

How is your water? But then, you say that coffee from your old brewer didn't have this problem.

How about your coffee? Have you changed the type of coffee you are buying recently? If you buy a dark roasted coffee, it's quite normal that some of the coffee's natural oils can be seen on the surface of the brew. But this wouldn't constitute a "dirty layer".

If anyone else has any experience of this problem or answers, please let us now.