South Korean stocks rose 0.81 percent on automaker and oil refiner gains on Friday but trading was volatile on investor caution before U.S. Federal Reserve Chairman Ben Bernanke's speech, analysts said. The local currency gained against the U.S. dollar. The benchmark Korea Composite Stock Price Index (KOSPI) climbed 14.37 points to 1,778.95, gaining for the second straight session. Trading volume was light at 306.2 million shares worth 4.86 trillion won (US$4.49 billion), with gainers topping losers 448 to 387.