Will the ammonia based products used for copper fouling remove copper oxide as well?

                               Thanx

Where do you have copper oxide ?  

If copper oxide is the same as the brownish patina on a penny – then yes.

If it isn’t, I haven’t a clue!  [:D]

Two "easy" ways to check for copper of any kind (including most oxides) is to either see if your patch comes out green after the suspected copper oxide has been exposed to one of the higher concentration bore cleaners (make sure not to use any copper containing brushes).

The second method is to take a small scraping and put the flake in one's scanning electron microscope [;)].

While of course I am being a little bit of wise ass ... could always be talked into a little free anlysis for any interesting project (assuming lab stays together).