When you buy that all natural peanut butter, there’s a puddle of oil at the top of the jar. Are you supposed to dump that out or stirr it into the peanut butter?
Stir it in, it’s just peanut oil.
If it’s got a layer of oil on top, it’s been in the jar too long, IMH taste preference. Go to a health food store and get some fresh-ground PB[ I salt mine just a bit, to bring out the flavor] Regular jarred PB never oozes oil because it’s been homogenized[or for the conspiracy-minded, the oil’s been sucked out before it goes in the jar] Don’t forget the pineapple preserves and seeded rye bread.
It’s because it’s not hydrogenated (which is a good thing, as Martha would say if she were still with us). Stir it in then put in the refrigerator so it doesn’t separate again. Then when you want to use it, pop it in the micro-wave for 30 seconds to make it spreadable again. Ummmmmmm peanut butter. 
My boss is kind of uber-picky about fresh foods. She has her peanut butter specially ground at the health food (I think) store. It really doesn’t cost much more than regular peanut butter, either…maybe a few cents. I don’t think I’ve ever seen any oil on top of hers.
Of course that could be because she eats it too quickly for it to rise to the top.
Any knowledgeable Dopers know if freshly ground peanut butter would have oil? If what Pictsie Pat says is so, then I didn’t realize peanuts themselves could be hydrogenated. Just curious, here.
Sylkyn if by “peanuts themselves,” you include peanut oil, then yes, peanuts can be hydrogenated. I can’t imagine the properties of peanut oil to be that much different from those of similar oils (vegetable, canola, coconut…)
Well, that’s why I am addicted to this site! Thanks for the information, iwakura43. Needless to say, I know ZIP about peanuts/peanut oil. It was just kind of confusing.
Now I think I am going to ask my boss if her peanut butter ever has oil on top…so I can sound like a smartass when I tell her why or why not! 
I often buy this kind so that I can pour off the oil. The bottom gets kind of hard, but it’s worth it to me to not have so much fat.
It’s my understanding that all-natural peanut butter doesn’t have the emulsifiers found in brands like Skippy that keep the oil from separating out. If you grind up your own peanuts and let it sit long enough you’ll get some oil separation-it’s harmless. You don’t have to stir it back in if you don’t want, but your peanut butter will be mighty thick.
Peanut oil is worth more than other oils so the non natural stuff has lots of the peanut oil removed and hydrogenated vegetable oil is used to replace the removed oil. Plenty of sugar and salt is also added.