The refinery converts oil into different types of petrol that can be used by other systems.

Oil Empire contains five petrol types.

Research provides permanent improvements to different parts of your empire, including production, capacity, value, costs and other systems depending on the research upgrade.

Some research requires a previous research item to be completed before it becomes available.

Where the option is available, remaining research time can be completed using Gold.

Factories produce troops used when attacking enemy outposts.

Factories unlock as you progress through Oil Empire's oilfields.