Rosberg fastest at Sepang
Nico Rosberg set the pace ahead of Sunday's Malaysian Grand Prix, but he had a number of rivals breathing down his neck.
Rosberg, who won the season-opening Australian Grand Prix a fortnight ago by a comfortable margin, finished quickest at the end of the two 90-minute Friday practice sessions at a steamy Sepang International Circuit.
The early championship pacesetter posted a lap time in his Mercedes of one minute 39.909secs, but with Ferrari's Kimi Raikkonen and Red Bull's four-time title holder Sebastian Vettel in close attendance.
Raikkonen, appearing strong at this venue where temperatures hit 34 degrees centigrade after a disappointing second debut on his return to Ferrari this season, finished just 0.035secs adrift.
As for Vettel, whose race at Melbourne's Albert Park ended after only a handful of laps due to a cylinder failure in the Renault engine, the 26-year-old finished 0.061secs down on German compatriot Rosberg.
Lewis Hamilton, who was quickest in the opening session, was down in fourth on the timesheet in his Mercedes, 0.142secs behind Rosberg, and with his car so far holding up.
After starting from pole position in Melbourne, Hamilton completed just two laps prior to his engine also suffering a cylinder failure.
Over the intervening period the team opted to execute a fix rather than going for a change as the engine forms just one component of the power unit this season.
Over the course of the campaign only five power units are allowed per driver, beyond which grid penalties start to apply, forcing Mercedes to seek a cure and so not compromise Hamilton later in the year.
Overall, the top six were covered by a fraction over two tenths of a second, with Ferrari's Fernando Alonso and former team-mate Felipe Massa, now with Williams, also in the mix.
Daniel Ricciardo, disqualified in Melbourne over a fuel irregularity with his Red Bull, was 0.367secs down on Rosberg, with a gap then of over three tenths of a second to McLaren's Jenson Button.
Max Chilton finished 3.7secs back in his Marussia in 18th, ahead of team-mate Jules Bianchi, with Caterham's Marcus Ericsson 20th and the last of those to set a timed lap.
Team-mate Kamui Kobayashi failed to complete a single lap in the second session due to a problem with the car's energy store.
Pastor Maldonado, who managed just two installation laps in FP1 before wisps of smoke emerged from his Lotus, also did not see any action in FP2 due to an apparent issue with the turbo.
Team-mate Romain Grosjean, who completed only four installation laps in the first session due to further problems with his car, at least completed 14 in the later run.
However, the Frenchman ran into gearbox issues and was forced to pit, leaving the team with further headaches after the trouble they encountered in Australia.
The duo started at the back of the grid in Melbourne such were there woes Down Under, before completing 43 and 29 laps respectively prior to suffering failures with the energy recovery system.
Such distances were viewed as minor triumphs at Enstone, but despite time since then to work on reliability, the issues are continuing.