Red Bull was back on top of the F1 timesheets at the end of the opening free practice session at the Malaysian Grand Prix, but it was Mark Webber, rather than Sebastian Vettel, who led the way after 90 minutes of running in sweltering conditions.
Despite the morning time slot, temperatures were already into the 30s by the point at which most teams decided that it was worth venturing out, having opted against too much early running in an effort to preserve their limited supply of tyres. Wear was clearly a problem, with almost every team suffering problems during the session despite opting to use the hard compound provided by Pirelli for their runs.
Webber was among the first to venture out for some 'proper' running, eventually holding on to top spot with a 1min 36.395secs best as others came and went. The Australian was pushed hard, however, as Melbourne winner Kimi Raikkonen got to within 0.068secs of the benchmark, despite having his running limited by a KERS issue that required a battery change in the early part of the session. Vettel, who initially traded times with his team-mate, completed the top three, a tenth behind the Finn, with Fernando Alonso fourth for Ferrari, just ahead of Mercedes' Nico Rosberg.
Lewis Hamilton and Romain Grosjean also took turns in P1 before the Red Bulls appeared, but had to settle for ninth and tenth in the final reckoning as Felipe Massa and the Force Indias of Adrian Sutil and Paul di Resta pushed themselves ahead. The Silverstone team, which sandwiched Massa in seventh, is laying a legitimate claim to be the fifth best team of 2013, as McLaren continued to struggle with its MP4-28. While not expecting miracles after a disappointing debut in Melbourne, Jenson Button and Sergio Perez could only manage eleventh and 13th in the opening session as the Woking team continued to explore its ride height issues.
The pair were split by Pastor Maldonado's Williams, the Venezuelan half a second slower than Button's best, while Nico Hulkenberg and Esteban Gutierrez put their Saubers ahead of the second Williams of Valtteri Bottas. The Finn, who ran a different configuration to his team-mate as Williams looked to address its poor start to the season, just edged the best of the Toro Rosso drivers, where Jean-Eric Vergne got the better of Daniel Ricciardo.
At the back of the pack, Giedo van der Garde emerged with 'division three' honours for Caterham, a couple of tenths faster than Marussia's Jules Bianchi.