Power and ICEs?

[nothing_cool]

I can't help but notice all the lights everywhere and wonder how they're powered. Someone in one of my FCs suggested Aether powered lights, but that wouldn't make sense to me for the Garleans, who focus on Magitek over magic. Is electricity a thing canonically?
On the topic of the Garleans, they use a lot of engines powered by Ceruleam, often in their mechs/amour suits. Do we have any sort of ideas as to what type of engine these are? Ceruleum powered things do often seem to have an exhaust pipe, but not much more than that. We see the big, flying hand thingies that have fans/turbines in them, but not much else.
Are there any other sources of energy or motive power such as steam or eletric motours?

[Cilia]

Ceruleum is essentially magical gasoline; as such it can be used for all the purposes gasoline is used and then some, and serves as the backbone of the Garlean Empire's power supply. All Garlean machina uses ceruleum unless otherwise noted (the Ultima Weapon used the Heart of Sabik, f'ex; even then it still supplemented its power supply with ceruleum if I remember right).

Though they can use magic, the Eorzeans still use ceruleum for certain applications; airships still run on the fuel, and all of Cid's consumer products implicitly use it as well.

Alternative fuel sources (steam, electricity) are in their infancy; ceruleum is more efficient, and the Eorzeans with the funds to develop such technology (Ul'dahns) are held back by their plutocratic government. (There is the beginning of a steam train in Thanalan, but because it would be a threat to Lolorito's business, it's incomplete and underfunded.) Ala Mhigo was said to be the most technologically advanced city-state before it fell to the Garlean Empire, but I didn't really see evidence of such during our time in Gyr Abania.

Past that, elemental crystals can presumably be used to replicate the effects of the element they are attuned to; a lightning crystal could be considered a battery, f'ex.

Most transportation in Eorzea is still done via chocobo and chocobo-drawn carriages, due to wealthy businesspeople (Lolorito) having a stake in it. Shipment of goods is done primarily via sea routes due to it being less dangerous and costly, however.

[Nightsword]

Ala Mhigo was said to be the most technologically advanced city-state before it fell to the Garlean Empire, but I didn't really see evidence of such during our time in Gyr Abania.

You're forgetting about the years long civil war in Gyr Abania prior to the Garlean invasion that had already destroyed most of the country's infrastructure, reducing it pre-industrial levels. It's something that still happens in our world, so it's believable in FFXIV that we don't see any signs of technology in Gry Abania. Though Gold Saucer is an example of Ala Mhigo technology and that place is one of the most modern advanced areas in the game.

[Theodric]

There's clockwork technology, too, as seen in Hingashi via some of the sentries in Kugane Castle. We also see clockwork devices within the remnants of Goug - AKA Ridorana Lighthouse. Nym also appears to use some manner of clockwork as Wanderer's Palace has visible cogs and doors are opened via a clockwork mechanism.

[Iscah]

The Garleans canonically use lightning aether for what we would recognise as radio communication.

CID
I'm going to put together a makeshift communications-jamming device. The explanation is like to get a bit technical, so bear with me.
Imperial forces communicate at a distance via electromagnetic waves. Simply put, voices are borne upon aetheric lightning energy that permeates the air.
Now, the hill-sized cluster of corrupted crystals to the west has been observed to amplify the selfsame energy. By making use of this property, we should be able to drown out imperial voices.

[Enkidoh]

I think the 'Ala Mhigo was the most technologically advanced of the Eorzean citystates' thing was just an old bit of 1.0 lore that was never taken further sadly and has for all intents and purposes been retconned.

As for the railway in Thanalan, I think it's been stated via several sources that it's actually magitek powered (as in, uses a cereleum engine) rather than steam - an npc at Black Brush station tells you that if you wait long enough, one of those "magitek powered conveyances" should arrive (as in, the train), although alas it never does, and the main FFXIV website also states about the development of the railway there being a melding of Ul'dah's minecarts with magitek technology implemented by "exiled Garlean engineers" (referring obviously to the Garlond Ironworks).

So as others have stated cereleum engines are used as the primary power source for powered vehicles and machinery - the cereleum engine itself is actually visible in most technologies that use it from my understanding, it's that weird spinning catherine-wheel like thing on the back of Garlean vanguards and juggernauts for instance. Which makes it very similar, although using a different fuel/power source, to the aeolipile, the very earliest form of powered engine known (an ancient forerunner to the steam turbine). Which is fitting given Eorzea's original setting was based very loosely on the ancient Greek citystates. But I digress...

[Apoptomon]

Lots of good points about Garlean stuff in here. As for the Eorzean city states, according to this early quest Limsa uses fish (or fishy-smelling) oil as fuel for streetlamps, and I at least assumed the others would use something similar (as with real-world pre-electric lighting) for their streetlamps and waymark-lanterns. As for what actually lights them, I don't think it's stated anywhere. It could be a fire or lightning crystal I suppose, or just a match. *shrug*