I'd like to suggest that we can get oil when working in space as a space miner. So basically when you break rocks on that asteroid in space there is 1/4 (so basically if you mine 4 rocks one of those will give you some oil) chance to get some oil (the number of oil units you'll get of course depends on your level).
Each time you get some oil a message would pop out "You found X units of mineral oil." just to make some sense, otherwise that's just a message and you actually get normal oil.
Just to make it more detailed, here's how much oil you should get depending on your level:
Level 1 - 5-10 units of oil
Level 2 - 10-20 units of oil
Level 3 - 20-35 units of oil
Level 4 - 35 - 50 units of oil
Level 5 - 50-65 units of oil
Level 6 - 65-80 units of oil
Level 7 - 80-95 units of oil
Level 8 - 95-120 units of oil
Level 9 - 120-135 units of oil
Level 10 - 135-150 units of oil
Could be of course decreased or even increased, that's just an example.
Now this is only because not many players like turf, so they basically have to buy oil since there's no other way to get it. Also, this would make more people go to space, so yeah.
