Lewis Hamilton turned the tables on Mercedes team-mate Nico Rosberg by setting the pace in a second practice session which brought more frustration for Sebastian Vettel at the Russian Grand Prix on Friday.
Championship leader Rosberg was three-quarters of a second quicker than Hamilton in FP1, but the world champion responded in ominous fashion at the Sochi Autodrom circuit.
Hamilton, eyeing a third successive victory in Russia and a first of the season, clocked a blistering lap of one minute 37.583 to top the timesheets ahead of Vettel.
Rosberg has won all three races so far this season and led the way with a lap of 1:38.127 in FP1, but was 0.867secs slower than Hamilton to finish third in the second session.
Vettel was second-fastest, 0.652 adrift of Briton Hamilton, but endured the frustration of spending much of the session kicking his heels after suspected electrical problems brought his Ferrari to a halt.
Four-time world champion Vettel, using a new internal combustion engine this weekend along with team-mate Kimi Raikkonen, was only able to run for half an hour of the 90-minute session.
Raikkonen was fourth in FP2, with Red Bull's Daniel Ricciardo fifth after giving the aeroscreen cockpit protection system a first outing in public on an installation lap before it was removed for the first practice session.
1. Lewis Hamilton (Mercedes) 1:37.583
2. Sebastian Vettel (Ferrari) 1:38.235
3. Nico Rosberg (Mercedes) 1:38.450
4. Kimi Raikkonen (Ferrari) 1:38.793
5. Daniel Ricciardo (Red Bull) 1:39.084
6. Valtteri Bottas (Williams) 1:39.185
7. Daniil Kvyat (Red Bull) 1:39.193
8. Jenson Button (McLaren) 1:39.196
9. Felipe Massa (Williams) 1:39.289
10. Fernando Alonso (McLaren) 1:39.400