I store the peanut butter upside down. When I'm ready for that jar, I put it in the microwave for 20-30 seconds upside down. I take it out and shake it a few times and then stir. By then normally almost all of the oil is sucked into the peanut butter and it's an easy stirring job. I haven't had any problem with it seperating after this. I use Wild Oats brand PB, in the plastic jars. Love it!
"The greatest danger for most of us lies not in setting our aim too high and falling short; but in setting our aim too low, and achieving our mark." Michelangelo Buonarroti