Lewis Hamilton took aim at Formula One champion Sebastian Vettel's run of five consecutive pole positions after topping practice for the Korean Grand Prix.
In cold, wet conditions at Yeongam, Hamilton shrugged off a poor run of form with a best time of one minute and 50.828 seconds to outpace McLaren team-mate Jenson Button by 0.104 seconds.
Vettel, 24, who was crowned Formula One's youngest ever back-to-back champion, was third fastest in his Red Bull car, ahead of Ferrari's Fernando Alonso in fourth. Hamilton finished fifth last week in Suzuka, underlining a difficult few months and is winless since July.
Sutil struggles Sahara Force India's Paul di Resta finished 10th while Adrian Sutil was 12th in the Korean GP Free Practice. Di Resta clocked 1:53.957, while his teammate Sutil finished with a timing of 1:54.392s.