This is the secret of the world to come. Our mitzwoth and Torah and all of our actions in this world create vessels through which we are able to receive HaShem's infinite light in the world to come. The more and finer vessels we create in this world, the more of HaShem's light we will be able to perceive in the world to come. HaShem's light is infinite and so the only limit on our experience in the world to come is the vessels which we create in this world.
[Oil is one of the names used to refer to Hochmah, wisdom, in the Kabbalistic literature.]