Drivers who track gas prices are in for an unpleasant surprise: The average cost of a gallon in the US rose 11 cents overnight to $3.11, reports the AP, citing data from the motor club AAA. The reason is no surprise: The Mideast is now engulfed in war, which has put the global oil market in what CNBC sees as a "worst-case scenario." Iran has effectively shut down the Strait of Hormuz, stifling a significant chunk of the world's oil shipments, and it continues to launch retaliatory attacks on neighboring nations' energy facilities. Brent crude, the international standard, rose about 9% to to $81 a barrel on Tuesday morning. How much more it rises—taking gas prices along for the ride—depends on how the war goes: