Oil is required to keep Daniel's lantern lit. The oil in the lantern will slowly burn until it is depleted, at which point the lantern will automatically go out and cannot be lit again until more is added. Oil containers can be found all over Brennenburg Castle, albeit less frequently than tinderboxes. They come in small, blue glass containers and shimmer faintly, making them significantly easier to find.
There are actually two versions of oil: a smaller container that fills approximately one-quarter (1/4) of the lantern, and a larger container which fills about half (1/2) of it. Large oil potions are absent from the main story (except for one bottle that rolls across a fallen down bookshelf during the revenge ending), but are still implementable in custom maps.
There are also larger barrel-like oil containers that can be found in several levels in the game. These are usually hidden in a corner of a room somewhere and will restore a varying amount, depending on how much oil Daniel currently has. The less oil Daniel has in his inventory, the more it will fill his lantern; it can restore anywhere from 25-100% of the lantern's total oil capacity.
There are a total of 37 oil potions in the game, not counting the large oil potion found in the revenge ending scene. This is enough to fill 9 1/2 lanterns worth of oil. There are also seven (7) oil barrels that can be found throughout the game.
- Next to Daniel's note to self.
- An oil can be found in a chest in the corridor leading to the entrance door.
- Another oil container can be found further down the corridor, closer to the door.
- An oil can be found in the "Old Tomes" section of the Archives.
- Another oil container can be found on a table at the part of the Archives furthest away from the entrance. It's close to a piano.
- One oil container can be found in the "Floor Plans" section of the Archives.
- One final oil container can be found in a corner of the room where you have to pull the books to open the door to the room where you get the Wine Cellar key.
- An oil barrel can be found in the corner of the room where you find the Calamine.
- An oil container can be found rolling across the floor to your right as you walk down the stairs.
- Another one can be found at the top of a shelf in the same room. It's quite difficult to reach.
- A third one can be found on a bookshelf in the main laboratory area, across the lab table.
- An oil container can be found in the room to your left as you enter the room where you see the Grunt.
- An oil barrel can be found in the room with the floor hatch.
- The one oil container in this area is located on a box next to a hunch of meat in the largest room.
- There is a oil container in a chest underneath the stairs.
- One oil container can be found in a smaller sub-room of the room where you find the explosive liquids. Four tinderboxes and a Laudanum potion can also be found in the room.
- Another oil container can be found in the northernmost part of the large room you get to after blowing up the debris blocking your way.
- A third one can be found in the room with the pigs hanging from the ceiling.
- An oil can be found on the shelf next to the locked closet door
- An oil container can be found next to the cracked window.
- There is an oil barrel in the room where you find the rod.
- There is an oil barrel in the room where you find the coal.
- There is one container in a cell at the end of the corridor that's on your left when you get to the stairs. It's opposite the cell where you find the hammer.
- An oil container sits on a chair in the main hallway.
- In a cell close to the cell with the hidden hole under the bed.
- There is an oil barrel in a cell just north of the potion you find on a chair in the hallway. The door is jammed, and you will have to use the hammer and chipper to smash the lock.
- There is one oil container hidden in the kitchen.
- In a tiny cell in the western part of the prison.
- There is one container in the back of a cell you pass by on your way to the Storage. Be aware though, as a Grunt roams this cell.
- One container can be found in a chest in the storage.
- The one oil container in this area is in the room to your right after you pass the door you need to crank open. It's beneath the stairs.
- One oil container can be found near the large tank where there supposedly is a man drowning in the water.
- Another one can be found at the western part of the Cistern, across the hanging bridge and near the water cranks and the note.
- An oil barrel can be found in the room with the gear controls.
- There is a large oil barrel in the room with the two levers.
- One oil container can be found beneath the hatch in the ceiling, close to Agrippa.
- One oil container can be found near the wall, across the bridge on the east side of the choir.
- Another one can be found opposite the broken down pillar that form a makeshift bridge.
- Following the path to the right as you get to the intersection, you end up in a strange room with an altar at the bottom. A container is located near the altar. (Note: This container has to be picked up before you collect the orb pieces, as the path there will have fallen down into the pit when you return from the cells).
- In the room up the staircase, one oil container can be found.
- An oil container can be found in the cell you wake up in.
- Another one can be found in the southernmost cell, where a note can be found.
This is the version of the Nave you reach after escaping the Cells.
- In the top left cell of the left wall of the chambers in the Nave.
- On the ground on the top floor of the right wall of the chambers in the Nave.
- As mentioned earlier, a large version of the oil potion can be found at the very end of the game, in the Revenge Ending. At the final part of the ending, Daniel walks through the Entrance Hall. While he does this, a large oil potion can be seen rolling across a tipped-over bookcase lying on the floor. If you're fast enough, there is actually enough time to pick it up. However, since the game is over, it is not possible to use this potion.