You can use oil to fuel lanterns, but you can also set a pint of oil aflame and throw it. You must first spend an Interact action preparing the oil, then throw it with a second action as a Ranged Attack. If you hit, it splatters on the creature or in a single 5-foot square you target. You must succeed at a DC 7 flat check for the oil to ignite successfully when it hits. If the oil ignites, the target takes 1d8 fire damage.