Admittedly the wintergreen we started off with was not a Lorann's flavoring, but some "other stuff" that was definitely an oil base that didn't mix well. We had to oust that one in favor of the Lorann's as it was, while still oil base, more soluable in PG and broke down with blender's alcohol better in liquids with more VG.
Essential oils, you will find, WILL NOT mix in VG. Actually, you'll find they separate within a half hour in VG.