The Oil Pump is a place where you can extract Oil. It's located in the middle below the Pyramid in the Underground City.
It has 17 levels overall, level 0 being the first and 16 the last. Each upgrade increases the speed at which you extract Oil and how much you can store. However, the capacity increases faster than the pumping speed, so the "time to full" will continue to increase.
Tips/Notes:
With a drop from a chest (chests give an hour of production), you can hold Oil over the capacity. E.g. at lvl. 6, when you hold 198/200 Oil, open the chest, get 12 Oil, now you can have 210/200 Oil. It allows you to build the Gravity Engine (Lvl.13) which costs 210 Oil.
It is also worth noting that the "time to full" when you hover over the current oil amount in the oil pump window, that the timer only displays a maximum of 24 hours.
Lvl.
Extracting Time
Capacity
Upgrade Cost
Chest/Gold
Excavation
Note
in seconds.
regular chests give 1 hour (3,600 seconds) worth of generation
gold chests give 4 hours (14,400 seconds) worth of generation