Red Bull's Sebastian Vettel topped the timesheets in the second practice session ahead of the Korean Grand Prix.
Vettel edged out Red Bull teammate Mark Webber into second position as he looks to build upon his victory at the Japanese Grand Prix last weekend.
Championship leader Fernando Alonso finished in third place ahead of McLaren's Jenson Button, who occupied fourth.
First practice session leader Lewis Hamilton slipped down the field into eighth spot.
