Ok, then do this -
Add Timer behavior to building.
When Building is created, start a recurring timer "AddOil".
On "AddOil" timer event, add 1 to Oil.
Timer is a much better option here than using "Every X second" or "Wait".
In "On timer" event you can do different checks - say, if building is upgraded, you can add 2 oil. Or you can stop the timer when player pauses the game etc.