Natural peanut butter doesn't contain added oils, but it does require regular stirring, especially when you first buy it. That can be messy and difficult. So each time I buy a new jar, I store it in my pantry upside down until I'm ready to use it. That mixes the oil better for easier stirring!
When you finally open the jar, use a butter knife to stir the oil throughout the jar until it's well mixed. Then store your mixed peanut butter in the fridge and the oils will not separate!