The Fuel Refinery is the building responsible for producing fuel inside the base. Its level corresponds to the level of the Command Center. As the level of your Command Center increases, the level of the Fuel Refinery increases automatically, and fuel production increases.

The highest level for the Fuel Refinery is 40, and it will not rise above that level even if the Command Center is upgraded further.

You can click on the Fuel Refinery to boost production either by using production boost items (20 items will be deducted at once to increase production for 8 hours). Or by spending 960 gold to increase production for 8 hours.