Renault's Robert Kubica put the Formula One title contenders in the shade with the fastest lap in Saturday's final South Korean Grand Prix practice.
The Pole, whose only race victory was in Canada with BMW-Sauber in 2008, lapped the hastily-completed and slippery new Yeongam track with a best time of one minute 37.354 seconds.
McLaren's 2008 champion Lewis Hamilton was second quickest, 0.048 slower, with Ferrari's double champion Fernando Alonso third and Red Bull's overall leader Mark Webber in fourth place.
The times indicated that four teams are on an almost equal footing in terms of pace ahead of a crucial race for the five men fighting for the title.
McLaren's world champion Jenson Button, who is 31 points behind Webber and needs a big result on Sunday, was seventh while Red Bull's Sebastian Vettel was the lowest placed of the five title contenders in 16th.
Vettel, third overall but level on points with Alonso who is 14 behind Webber with three races remaining, has looked far from impressive on the dusty anti-clockwise track.
The 23-year-old German, who will be chasing his ninth pole of the season later on Saturday, was fourth and seventh in Friday's two sessions.
Kubica, making full use of the Renault 'F-duct' on the circuit's long straights, had been tipped to do well by Hamilton earlier in the week.
"I don't think we are going to be the fastest on the straights because the Renaults and the Force Indias seem to be very quick on straights," he had told Reuters.
"Whether or not we will be quicker than them I don't know."