A big shift in the oil trade may signal the petrodollar's decline, which would be bad news for US financial power and good for BRICS nations like China and Russia.

• For the first time since 1985, the US bought no oil at all from Saudi Arabia for a full month.
• The stoppage came from the US-Iran conflict, which shut down crude flows through the Strait of Hormuz.
• US refiners like Phillips 66 switched to American and Venezuelan oil instead, with Venezuelan imports jumping sharply.
• The worry is that if Saudi Arabia can't reliably sell oil to the US, it may drift toward China and Russia and drop the dollar.
• Official talk of a US "victory" over Iran clashes with the reality that Iran keeps launching strikes and blocking Gulf shipping.

Outlook: US-Saudi oil imports are expected to partly recover this month, but the bigger risk is Saudi Arabia leaning toward BRICS and away from the dollar.