Refining allows the building of power plants which increase factory production but cause large amounts of pollution.
It is a prerequisite of combustion and plastics.
Civilopedia
Mineral tar and petroleum have been known throughout history, but little use was found for either until it was discovered through Chemistry that oil could be Refined into chemicals with a wide variety of uses. The primary application of oil derivatives was as fuel for internal Combustion engines that powered the Automobile and other machines. Oil had to await the Industrial Revolution before its potential could be realized, because large Corporations could afford the investments in Automobile production and Refining that were required.