The most natural nut butters and some butters which aren't nuts - peanut, sesame, cashew, almond - usually come with the oil separated and floating on top. In some cases standing the jar on its lid will do it. But often that won't do it. To solve this problem I intend to look for a paint store going out of business to see if I can get a deal on a paint can shaker. Those things will take a can of paint that's totally separated and blend it all together like new. Once I get one, I'll have to take it to a shop to have it modified for jars and no more will we have to go through the tedious process of mixing it all back together by hand which is always sort of half done.
That reminds me of when my son Kelly was a baby. I used to throw him up and down and shake him all the time. And then we learned that that can cause brain damage but he was already beyond the shaking age when that was in the news so the damage had been done. People got quite concerned about how he'd turn out. To add to their concern, I started confessing that I used to bring him to paint stores with me and to occupy him while I was shopping, I'd strap him in a paint shaker and turn it on and leave him there. I'd add that once I forgot him and drove off without him and only came back an hour later and he was still rattling away in the paint shaker. I was especially delighted that some would actually believe me - for a minute.