Castrol oil is generally best placed in a car''s engine to ensure optimum performance. We think that you mean Castor oil. This, used as an enema or taken by mouth, stimulates your intestine and, as the nerve supply to this is shared with the uterus, has been used to induce contractions and labour. We would not advise you to try anything to induce labour at 36 weeks, as the baby is still a little premature. Full term is from 37-42 weeks.