"Natural " peanut butter has that layer of floating oil on top because it has not been chemically altered (also means low in trans fat). You should see that as a good sign. The natural oils in peanut butter are unsaturated and, like olive and canola oils, can actually help to lower levels of bad cholesterol and raise levels of good cholesterol. Most natural peanut butters are made only with ground peanuts and a little salt. Some have extra oil added to make the butter creamier; some have sugar added.