Oil type flavorings will dissolve in both pg and vg....this separation just scares me. I have never seen it. VG and PG are bipolar solvents. That means they can dissolve both water based materials and oil based materials. For a material to be able to separate in a time frame for you to witness it, is scary. You don't know how the separating material will react in contact with a coil's heat range. BTW, I stick with the perfumers Apprentice. They are just 30 mins away in Scotts Valley. They also have a real chemist on board along with the proper lab equipment to check what they are selling. And they are e-liquid flavoring friendly unlike some flavor houses.