I use different oils depending on the time. For morning/day I use Flax Seed oil. If I use that at night it keeps me awake - for hours and hours. In the evening I use coconut oil because it always makes me feel sleepy afterwards.
If I ever absolutely positively need to sleep til noon (like catching up on lost sleep etc) OP with coconut oil before bedtime is the only thing that works for me. Even Nyquil can't do that for me.
There are major differences between the effects of different oils, so it's good to try new ones.