How we can get some more oil?
First way - build oil derrick. It give about 50 oil per 4h. Or 300 oul per 24h.
Next way - excange 1 energy to 1 oil. Take a shovel and start digging.
Some free oil 1-4 per action you can get when your neighbors come to your town and tending crops or grooming animals. More active friends, more oil you can get from them.
Other exchange - you can buy 1 oil for 50 gold. Buy white bunnies from arctic, 200g each. Place them, and get 2 oil for it, then sell them back for 100g each.
Next opportunity to get oil from trees.
Lemon cost 6bn each. Buy you can get it from other players. It give you 1 oil every 3 day. Or 0,33 oil per 24h.
Orange cost 12bn and give you 10 oil per tree every time when it ripe.
Plum cost 18bn and give you 20 oil per tree every time when it ripe.