That's roughly the number of barrels of oil passing through Egypt's Suez Canal and Sumed pipeline daily, about 5 percent of global consumption. Oil futures surged on financial markets last week amid rampant political violence in Egypt. Though the bloodshed prompted Egypt's army to step up canal security, a closure wouldn't be unprecedented. Egypt blocked the canal from 1967 to 1975.

The turmoil of the Arab Spring -- Libya's production is still down -- could again bring the region's volatile geopolitics back to U.S. gas pumps.