Heads up, I've put way too much thought into how oil works in murder drones and why the DD's need it because I'm a giant nerd and I'm high on pain meds.
The 'Oil' that the drones bleed has 3 major components.
A powerful, sweet tasting non-polar solvent which is the actual oil.
A soup of metals and minerals held either in suspension or solution within the oil.
Sci fi nonsense repair nanites, also in suspension.
In this way Drone Oil is an example of biomimicry. JCJ wanted a system that would regularly ferry compounds across a drones body so they literally just made robot blood.
Their usage of a Non-polar solvent is actually the reason why injesting water is so deadly to worker drones. As a strong polar solvent water is really good at dissolving things drones would prefer to remain intact. They mix as well as oil and water, lol.
Humans would suffer similarly grizzly fates if they tried drinking a strong non-polar solvent like Benzene. Don't drink Benzene by the way, I don't care how sweet it smells it will literally dissolve your nerves.
The drones drink this solvent in the same way as we drink water. Its extremely easy to get a hold of, can be produced in a factory at scale and does almost nothing to satiate a hungry DD or Solver Drone.
Notice I didn't mention oils use as coolant once? Thats because it would be terrible at that job. DD's need the oil of course but not much more than the average worker drone, what they really craved are the repair nanites.
Disassembly drones don't overheat and die when they're starved of Oil because they literally use oil as coolant. They overheat and die because for all their lethality Disassembly Drones are actually horribly designed.
Cyn stuffed every weapon, doodad and tool she thought was cool into her murder pets; forgot she needed to leave room for the essentials; did the bare minimum to get them functional and then juiced them on absurd amounts of repair nanites as a "temporary solution" pending a redesign she was too lazy to actually bother doing.
Their vital systems were constantly on the verge of collapse and the only thing that kept them upright was healing from their repair nanites. If they ran out of nanites they would stop being able to keep repairing their undersized and overstrained systems and would suffer miserably until something important (usually but not always their vestigial coolant loop) broke down completely and killed them.
Things were so bad that the murder drones experienced chronic pain of increasing serverity every day that went by without gorging themselves. This is one of the main reasons N was so manic when he hunted, even without the reward loop simulating euphoria after killing someone the sheer relief was indescribable.
The worst thing is this wouldn't even be a problem if the DD's repair nanite fabricator was large and powerful enough to sustain them in periods of low activity. After all, every Worker Drone had a basic nanite fabricator built in as standard which could keep them going through superficial injuries. Thats why it wasn't unusual for Uzi and Thad to recover after being stabbed in the pilot.
Unfortunately Cyn had to choose between giving her murder pets a nanite fab that worked or a snatched waist.
As you can clearly see, she made her choice. And as a result the DD's didn't even have a nanite fab at all. They were entirely dependent on getting their nanites from external sources and on Copper 9 that meant eating worker drones.
N had it especially bad because He quit eating living drones cold turkey after episode 1 and survived off of what he could scavenge from corpses and what donated nanites he got from outpost 3. This was enough to keep him from dying but not enough to keep him from feeling like his body was slowly unravelling.
Naturally N didn't tell anyone about this because he's almost incapable of telling people when he's struggling with anything. Traumatised dog thing.
The truth only came out by accident. During N's first maintenance appointment at outpost 3 one of the technicians noticed N was wincing a lot during stretching exercises and when asked if he was in pain N responded "No more than usual!"
The tapestry of lies sort of unwravelled from there, even in spite of N's best attempt to slap a brave face back on.
V on the other hand kept sporadically hunting. She just went on long trips far from outpost 3 when the pain got intolerable. Prefering to target scap bandits and other violent criminals when she could in an attempt to assuage the guilt that life in a functioning community was ressurecting.
And of course V also never told anyone about her pain because she HATED showing weakness or vulnerability in front of others. Even when refusing to do so was actively self destructive.
Neither of these goobers could easily unlearn a lifetime of bad habits.
When Uzi found out about all this bullshit she threw a truly MYTHICAL fit. Her boyfriend and kinda sorta girlfriend had been dealing with chronic pain caused by Cyns psychotic design decisions and they never even felt it necessary to tell her?!
Yeah, someone was sleeping on the couch that night.
Thankfully Uzi was an engineering genius and her father was both the head of the colony and also a genius. Between both of them and the maintenence team they were able to devise a procedure for swapping out the DD's undersized generators, radiators, vents and motors with actual working replacements.
Doing so came at the cost of a LOT of the weapons and Systems Cyn had crammed in there. That said neither drone had made a habit of fighting with anything other than the SMG's, rockets, lasers, claws and swords so it was no terrible loss. V DID find room for the bubble wand though, because of course she did.
Sadly supplying the nanites needed to keep the DD's Solver bio organic matter alive would have been completely infeasible so the robot vampirism could not be cured outright. That said the treatment WAS successful in resolving their pain and even reduced their rate of oil consumption at the same time.
The only real complication resulting from the surgery was when N broke into the home of his technician at 3 AM to deliver her a hand drawn thank you card. Poor girl woke up to a murder drone smiling at her in the darkness of her bedroom and almost short circuited.
