Claims have been circulating on social media that the United States has only about two weeks of oil left. The calculation appears to compare the 286.6 million barrels currently held in the Strategic Petroleum Reserve with roughly 20.7 million barrels per day of U.S. petroleum demand, producing a figure of about 14 days. But that does not describe how the U.S. petroleum system works, and even the units are mismatched. The SPR holds crude oil, while the 20.7-million-barrel figure represents total petroleum products supplied, a broad proxy for consumption…