Lewis Hamilton completed a clean sweep of fastest times in Korean Grand Prix Friday practice as Mercedes again took the fight to Red Bull.

In another strong hint that the champion team will face tougher opposition this weekend than of late, Hamilton not only set the outright pace with a 1m38.673s, but was also very positive about tire life over later long runs.

Sebastian Vettel was 0.108 second down on Hamilton in second place. The runaway world championship leader, chasing a fourth consecutive Formula 1 race win this weekend, waited much longer than anyone else to move to super-soft tires, jumping to second when he did so. That denied Mercedes a one-two, with Vettel edging Nico Rosberg by 0.016sec.

Mark Webber had been Hamilton’s main rival early on, as the pair swapped first place several times. The second Red Bull ended up back in fourth, but was within 0.063sec of its sister car.

Felipe Massa was Ferrari’s pacesetter in fifth, two places ahead of teammate Fernando Alonso. Romain Grosjean’s Lotus was in between them. The second Lotus of Kimi Raikkonen got straight back out after its morning crash and went eighth.

Despite a cockpit niggle, Jenson Button was ninth for McLaren, ahead of very-closely matched Force India duo Adrian Sutil and Paul di Resta, who were just 0.001sec apart.

No one repeated Raikkonen’s trip into the wall, but both Caterham’s Charles Pic and Sauber’s Esteban Gutierrez had spins during the afternoon while Alonso visited the grass on his final lap.

Pos Driver                Team                   Time        Gap    Laps 1. Lewis Hamilton        Mercedes               1m38.673s           31 2. Sebastian Vettel      Red Bull-Renault       1m38.781s  +0.108s  30 3. Nico Rosberg          Mercedes               1m38.797s  +0.124s  32 4. Mark Webber           Red Bull-Renault       1m38.844s  +0.171s  35 5. Felipe Massa          Ferrari                1m39.114s  +0.441s  30 6. Romain Grosjean       Lotus-Renault          1m39.226s  +0.553s  34 7. Fernando Alonso       Ferrari                1m39.444s  +0.771s  31 8. Kimi Raikkonen        Lotus-Renault          1m39.757s  +1.084s  33 9. Jenson Button         McLaren-Mercedes       1m39.774s  +1.101s  2910. Adrian Sutil          Force India-Mercedes   1m40.006s  +1.333s  3411. Paul di Resta         Force India-Mercedes   1m40.007s  +1.334s  3412. Sergio Perez          McLaren-Mercedes       1m40.152s  +1.479s  3113. Esteban Gutierrez     Sauber-Ferrari         1m40.186s  +1.513s  3314. Nico Hulkenberg       Sauber-Ferrari         1m40.210s  +1.537s  3415. Jean-Eric Vergne      Toro Rosso-Ferrari     1m40.446s  +1.773s  3016. Daniel Ricciardo      Toro Rosso-Ferrari     1m40.552s  +1.879s  2617. Pastor Maldonado      Williams-Renault       1m41.117s  +2.444s  3518. Valtteri Bottas       Williams-Renault       1m41.289s  +2.616s  3419. Giedo van der Garde   Caterham-Renault       1m42.461s  +3.788s  3620. Charles Pic           Caterham-Renault       1m42.798s  +4.125s  3521. Jules Bianchi         Marussia-Cosworth      1m43.108s  +4.435s  3122. Max Chilton           Marussia-Cosworth      1m43.441s  +4.768s  29