Depleted Tanks is a written note found in The Knife of Dunwall.
Transcript[]
Frank, I told you to have this thing replenished with a full tank at all times! We have a shipment coming in soon and this crane better be working by the time it arrives or someone will be demoted to sewer cleanup.
Cainin
Location[]
It can be found on the crane oil intake machine in the mission A Captain of Industry.