On a scale of 1 to 5 (because 1 to 10 systems always end up a "everyone chooses 7 because anything lower might as well be a negative") with 1 being completely annoying and 5 being acceptable:
Enlightenment age: 1 - Obviously an age that is not designed for grinding oil, get to industrial age for more oil if you want it.
Industrial age: 2 - Okay. You've got more oil now, which is nice. You still match in raids against enlightenments and industrials that are basically enlightenments though, so you come across a lot of 0 oil bases, which is still very annoying. Even raiding an enlightenment that does have oil can be an occasional waste of time. Even your reward for destroying all of an enlightenment's oil buildings is awful: it's 50 oil, wow. Your average oil raided is still something like 500 to 800 oil average, which is awful. If you want even more oil, upgrade to global.
Global age: 3 - Pretty much everyone you raid against has oil now, except the industrials that are basically enlightenments or the oddball 0 oil global players who are basically either crazy, age rushers, people with a ton of crowns, or cheaters without a clue of how the game works. Your average oil raided without going for precise picks on oil can easily be 1k+ oil now, which is a lot better.
Atomic age: 3 - Pretty much the global age experience, but even more oil. Average oil from just aimlessly raiding can waver from 1k oil a raid to something like 5k+ oil on the loaded base. Oil wells can rake in about 5k+ oil every ten hours with an oil blessing, Amelia research, and max current level oil wells, which is also a nice passive benefit. Means you make about 80k average oil a week doing literally nothing.