If you don't know how to set Variable voltage ooze battery, read this thread on.
For pre-filled oil cartridges, set your pen to 3.3V.

Prefilled 510 thread cartridges require lower temperatures because the material is thinner and easier to heat. We recommend starting at the lowest voltage, 3.3V, and moving up to 3.8V if it's not giving you enough of a hit.

Here is a video from Joe Robichaud