Oil flows upward in the wick of a lantern because of liquid property called

Capillarity "Capillarity causes the part of the surface of a liquid in contact with a solid, to be either elevated above (e.g. water), or depressed below (e.g. mercury), the rest of the surface. This trait is named for the behaviour of liquids in capillary tubes placed perpendicular to the surface. The forces operating within capillarity are cohesion, adhesion, and surface tension."