The oil may help, but I have found that soaking the tail for a few minutes in a tub of water will help loosen the stuck shed, and I have very gently used my fingernail to sort of pick at the retained shed. Also, when the tip is soaked, try softly rolling the tail tip to loosen it even further. You will have a mildly annoyed snake, but it beats the alternative of possible infection of necrotic tissue.