An interesting fact to consider is that the US stockpile (the Strategic Petroleum Reserve) is reported as the total of sour (high sulfur) and sweet (low sulfur) crude oil. The sweet stock makes up about 1/3 of the reserve and hardly varies at all. This is because US refineries are virtually all configured for sour crude: due to a mistaken belief in the 1990s that sweet crude was running out, the industry bet the farm on sour crude refining, and if sour crude runs low, it's extremely economical to switch.

As a result, almost all the draw from the SPR is of sour crude (currently ~5 million barrels/week). However, you can't just use up all the reserve because as levels get lower brine must be pumped into the storage chambers to retain pumping pressure, and the more brine that is pumped, the more the output quality declines.

The weekly reports indicate a total in the SPR of about 300mbb, of which ~100 are sweet and 200 sour. But for the reasons above, output becomes unusable one the sour levels fall to ~140-150mbb, at which point there is almost certainly a severe diesel supply shock. At current drawdown rates, that would be sometime around October/November, right in the middle of harvest season when demand for diesel is highest.

There's more complexity to this than I want to type out in a HN comment, but not that much more. Draw your own conclusions.