Walterjn That is not the issue as reported and I know how fuel is made. The shortage is due to many reasons but is also area-dependent. One reason Arizona is having a problem is the price of diesel surrounding AZ. Trucks can reduce their cost of fuel by filling up completely in AZ vice CA, some report by over $200. Another issue is the wear and tear on roads as trucks may now drive at max or slightly overweight limits because they are topping off. True trickle-down economics to use a term from the old days.
Coupled with reduced truck drivers stretched to work longer hours since the US "waived" some of the rules from early COVID days, hauling fuel is low. Throw in high prices due to low supplies and there has not been a priority to turn out diesel over gas.
Add in rising fuel costs hurts the shipping industry as they typically contract for work months in advance when diesel was significantly less, a $200 savings is a big deal.
And round and round we go.