any instant oils don't apply to mobs but use the oil, this is also an issue with potioncore reborn's explosion, lightning, and other instant potions.

I've just released the fix in version 3.2.1.
Closing issue

Stale issue message

Hi,
I've fixed this issue in the newest version in development. This seems to be because instant effects aren't properly being applied when oil effects are applied.
It will be in the next update.