Lewis Hamilton went quickest in second practice of the Malaysia Grand Prix, though the session was far from rosy for Mercedes' drivers' champion.
Hamilton's first practice session was wrecked after Mercedes engineers were unable to follow his telemetry in the pit lane, and the world champion missed around half an hour of FP2 as the team looked to fix his car.
Ominously for the field, Hamilton's first lap with the softer compound of tyres on resulted in a time of 1:39.790 – the only sub-1:40 lap of the weekend so far.
Valtteri Bottas and Felipe Massa got good lap distance under their belts, with the Finn also topping the speed trap results to suggest a good weekend for the British constructor lies ahead.
However, elsewhere in the race for second place in the constructors' championship, Red Bull and Ferrari have work to do after frustrating sessions.
Kimi Raikkonen was second quickest in the session, 0.373secs off Hamilton's pace, but the veteran complained of a lack of grip throughout, an issue which also affected team-mate Sebastian Vettel as he spun out at turn 11 – where Manor's Roberto Merhi also went off-track.
Red Bull's weekend has been dominated by their row with Renault, and reliability again hit them. Daniel Ricciardo managed just eight laps in the session, while Daniil Kvyat ended the session complaining of an issue in his power unit.
FP2 classification:
1.Lewis Hamilton (Mercedes) 1:39.790
2.Kimi Raikkonen (Ferrari) 1:40.163
3.Nico Rosberg (Mercedes) 1:40.218
4.Daniil Kvyat (Red Bull) 1:40.346
5.Valtteri Bottas (Williams) 1:40.450
6.Felipe Massa (Williams) 1:40.560
7.Sebastian Vettel (Ferrari) 1:40.652
8.Max Verstappen (Toro Rosso) 1:41.220
9.Marcus Ericsson (Sauber) 1:41.261
10.Daniel Ricciardo (Red Bull) 1:41.799