Typically some of the oil in peanut butter is exchanged with artery clogging partially hydrogenated vegetable oil so the oil will not separate. This has been the norm for years. Another advantage to adding trans fat to peanut butter is that it will not go rancid at room temperature so it doesn't need to be refrigerated. Now of course we know that trans fats are evil artery clogging Frankenfoods that will kill you and your children in their sleep so many peanut butters are made without them and heavily promoted as a healthy alternative. One type is old fashion peanut butter. Without saturated fats the oil floats to the top while the peanut butter solids settle on bottom and turn to cement. The trick with this peanut butter is to somehow mix it up (easier said than done) then keep it in your fridge to keep it from re-separating and going rancid. When my parents found jars of PB with oil separated in my pantry and in my fridge they commented, "what the heck? I thought they quit making this crap decades ago! would you like me to pick up some real PB next time I'm at the store?" I find warming the PB slightly in the microwave makes it easier to mix. I always wondered what would happen if you put a jar of old fashion peanut in the paint mixing machines at hardware stores that violently shake cans of paint. If it works I think there should be a law that every Whole Foods grocery store should have to install one, otherwise they should have to lower their prices so people other than celebrities, yuppies, and Republicans can afford to shop there. But I digress.... The other trick is to mix in palm oil to keep the oil from separating. Years ago everyone was convinced that Palm and coconut oils were bad and that hydrogenated vegetable oil was the way to go but now Palm and coconut oils are getting a reputation for being health foods. Kind of like in the movie Sleeper where in the future scientists discover that smoking is actually good for you. But I digress... What was the question again? Oh yes, if it is old fashion PB than mix it back in then keep in your fridge. If it is just a few drops of oil that separate from PB stabalized with trans fats or palm oil it doesn't really matter. In any case peanut butter is great! My favorite is a PB sandwich with apricot jam, makes me hungry just thinking about it. bon appeteit!
I agree with @satanheadbangstometal - if you dump out the oil, your peanut butter will become dry and flavourless.
Mix back in with the peanut butter. Mmm.