Mark Webber just edged Kimi Raikkonen to the fastest time in the first practice session for the Malaysian Grand Prix, with the Red Bull 0.068s quicker than the Lotus.
Webber's best time of 1:36.935 was set earlier in the session than Raikkonen's lap after the Lotus driver spent most of the first hour in the garage having his KERS battery replaced due to a sensor issue. When Raikkonen returned to the track the Australian GP race winner was immediately on the pace, setting a 1:37.003 on his first timed lap as Lotus continued its strong start to the season.
Sebastian Vettel was third fastest, 0.169s off the pace and ahead of Fernando Alonso and Nico Rosberg in fourth and fifth. Adrian Sutil again displayed impressive pace in the Force India with the sixth fastest time ahead of Felipe Massa, team-mate Paul di Resta and Lewis Hamilton, who finished his session radioing his team to tell them his rear tyres were "destroyed" after 18 laps on the hard compound. Romain Grosjean rounded off the top ten over 0.9s off his team-mate, although Lotus did have a number of upgrades to trial during the session that may have taken the focus off fast times.
Outside the top ten, Jenson Button was 1.2s off the pace in the McLaren as it looks as though the team is set for another tough weekend. A puncture added to his problems, meaning he had to use a second set of hard compound tyres towards the end of the session that would usually be reserved for FP2. Pastor Maldonado was 12th fastest as Williams showed the first signs of a recovery, finishing the session ahead of McLaren's Sergio Perez who was 13th.
Nico Hulkenberg was the highest-placed Sauber driver in 14th ahead of team-mate Esteban Gutierrez, the second Williams of Valtteri Bottas and the Toro Rossos of Jean-Eric Vergne and Daniel Ricciardo.
Caterham's Giedo van der Garde led the battle of the backmarkers, setting a lap 0.2s clear of Jules Bianchi's Marussia. Charles Pic and Max Chilton finished in 21st and 22nd.