Im not quite sure what you mean. This refinery uses the furnaces cooling output, its exhaust heat and recycles the heat of refined fuels. That being said, there is indeed more potential that could be utilised with a more sophisticated heat exchanger and some other tricks. At some point I might update this refinery, but Im already working on another one which is more than double as fast.

you could done increase even more by tap into the diesel furnace of hot fluid output because you just dump out in the air it kinda waste of potential