SEPANG - World champion Lewis Hamilton was unbeatable even in a misfiring car as he topped practice at the Malaysian Grand Prix despite mechanical problems on Friday.

The Mercedes man spent much of his time in the garage and departed first practice on a moped, but he still managed to set the day's quickest time by nearly four-tenths of a second. The performance at a sun-drenched Sepang underlined the superiority Hamilton showed in winning the season-opener in Australia as he sets out to secure a third world title. "It was an amazing job by the guys to get me back out this afternoon -- particularly here in such tough conditions, so I'm very grateful to them," he said.

Hamilton managed just four laps of the 90-minute first practice before he was told to halt his Mercedes W06 and hitched a lift back to the pits on the back of a moped. His problems continued in the second session as he sat out the first 40 minutes and then quickly had to return to the garage when his team could not see his telemetry data. Hamilton then re-emerged to set a field-scorching lap of 1min 39.790sec -- before returning to base shortly afterwards complaining of gear problems.

Daniil Kvyat was fourth-fastest in his Red Bull followed by the Williams drivers, Valtteri Bottas and Felipe Massa, and Ferrari's four-time world champion Sebastian Vettel.

Pastor Maldonado had a truncated second session after bodywork came loose on his Lotus, and Roberto Mehri spun into the gravel on his first day of action for Manor. Ferrari's Vettel followed Mehri off at Turn 11 before continuing, while Fernando Alonso also had some excursions off the track in his McLaren.

Alonso, who missed the Australian Grand Prix after a crash in testing, was 16th quickest, one place better than team-mate Jenson Button in another torrid day for McLaren. Manor's Will Stevens and Mehri propped up the timesheets but it was nevertheless a positive day for the new team, who failed to get out of their garage in Melbourne.