Oil should never be considered a renewable resource... Well, technically it is renewable but over an extremely long and impractical period of time. ;-p
Ofcourse, the world is infinite so just walk out further and find more oil or ores. So for the scope of this, game everything is already unlimited but I don't like the idea of resources randomly respawning without being seeded by some realistic method.
Like in the real world, oil cannot sustain a modern industrial civilization but since our species existence is but a brief moment in the history of this planet, it makes sense that there is plenty of oil for now. Eventually we need to transition beyond a dirty industrial period to get to a cleaner green period. Like now, hydro, geothermal, solar, wind, and algae are probably the way to go in the long-run. Will nuclear and natural gas be a thing in the interm? Not sure what's planned but it would be interesting if some radioactive ores existed in the game. I wonder if cows and composting might lead to natural gas capture.
Edit: Just noticed your comment on ethanol @ArcticuKitsu.. Yes. that would be cool too. with corn being a thing. that would offer a good alternative to oil and gas, albeit less efficient but more renewable.
Here's the progression i see:
Stone -> bronze -> iron -> steam industrial -> oil industrial -> high tech -> green tech