Answer: Some thoughts. These all fall under the umbrellas of mechanics & practicality, economics, and safety. 1. Refinery units are big. This is because they have to achieve a lot of throughput to be economical and satisfy a good chunk of local demand. A crude distiller which can process more. Even if our refineries are doing it as fast as they can, they’re producing a lot less than they were just a couple of years ago. In fuel refining circles there’s a phrase that gets thrown. Five refineries have shut down in the United States in just the past two years, reducing the nation’s refining capacity by about 5 percent and eliminating more than 1 million barrels of fuel per.