Most diesel refineries are on the east coast and will be shut down by October. Someone in the business said a chemical necessary to the process will be gone by then due to “supply chain issues.” I do know that that was one of the things the railroads were going to quit shipping.
Sorry I don’t have more substantial information. I don’t suppose it will be easy to get any sauce for this. If anyone has a relative or someone they know in the business it would be great to get more information.
A possibility: Refineries use (natural) gas to produce hydrogen, which they then use to remove Sulphur from diesel. The spike in gas prices in late 2021 made that process prohibitively expensive, cutting diesel output.
https://www.washingtonpost.com/business/energy/the-oil-price-rally-is-bad-the-diesel-crisis-is-far-worse/2022/03/14/e207748a-a36c-11ec-8628-3da4fa8f8714_story.html