New Delhi, April 18 -- Oil prices dropped back to where they were in the early days of the Iran war, and U.S. stocks raced to another record Friday after Iran said the Strait of Hormuz is open again for commercial tankers carrying crude from the Persian Gulf to customers worldwide.

The S&P 500 leaped 1.2% to an all-time high and closed out a third straight week of big gains, its longest streak since Halloween. A freer flow of oil could take pressure off prices not only for gasoline but also for groceries and all kinds of other products that get moved by vehicles. It could even ultimately help people pay less on credit-card interest and mortgage bills.

The Dow Jones Industrial Average surged as many as 1,100 points before paring its gain...