The US dollar index (DXY) closed last Friday at 99.32. WTI crude ended at $100.39 per barrel. Nearly three months into the US-Iran war, the dollar and oil have been rising together. Textbook economics says this should not happen. The textbook rule For decades, the US dollar and oil moved in opposite directions. From 2002 to 2014, the rolling correlation between the DXY and WTI crude was negative.