It goes something like this. The refiners have forecasting tools that predict what the supply situation is going to look like. They are going to buy certain crudes and make certain products. Each day, they look at their inventories on site, and they get a schedule of shipments from the pipeline scheduler. They will go to a morning meeting with operations and adjust cut points and various operating parameters to meet the immediate demand situation. If they have a local rack, and diesel is being pulled down while gasoline is steady or rising, they will shift production to diesel if they can. If they are already in a max-diesel mode, they will raise the rack price or put customers on allocation. I can tell you that customers hate allocation more than they hate seeing prices go up.

That can have them shifting production back and forth between gasoline and diesel more than once a week. That's not common, but it happens.