Renault's Robert Kubica took top honours Saturday in the final practice session ahead of the inaugural Korean Grand Prix, in which less than a tenth of a second separated the first four finishers, dpa reported.
The Pole completed the 5.62-kilometre course in one minute, 37.354 seconds, 0.048 seconds ahead of McLaren-Mercedes driver and former champion Lewis Hamilton in second.
Two-time champion Fernando Alonso was third in his Ferrari at 1:37.426 while Red Bull's Mark Webber was fourth at 1:37.441 at the Korean International Circuit in Yeongam, 400 kilometres south of Seoul.
Webber, who is leading the championship standings, finished first in the second practice session while Hamilton led the pack in the first session Friday.
Mercedes GP's Nico Rosberg came in fifth in Saturday's practice, followed by Alonso's teammate Felipe Massa and Hamilton's teammate and defending champion Jenson Button.
The worst performer among the five world champion contenders - Australian Webber, Spaniard Alonso, German Sebastian Vettel and Britons Hamilton and Button - was Renault's Vettel. He could do no better than 16th place in the 24-driver field, finishing with a disappointing 1:39.78.
Concerns that the drivers would encounter problems on the brand-new course, whose track surface was only finished two weeks ago, proved groundless.
Qualifying was scheduled for later Saturday, ahead of Sunday's Korean Grand Prix, the 17th race of the 19-race season.
Webber leads the standings with 220 points, ahead of Vettel and Alonso, who have 206 points each. Hamilton and Button are also still in the frame with 192 and 189 points, respectively.