Sebastian Vettel set the pace in second practice for the Russian Grand Prix, as Ferrari started the weekend with the edge over Formula 1 rival Mercedes.
Vettel, whose team-mate Kimi Raikkonen led the way in first practice, used a fresh set of ultra-soft Pirellis to clock a 1m34.120s at Sochi.
The German reported an "engine hesitation" on his outlap and after a conservative first flying lap, put the hammer down on the second to go 0.263 seconds quicker than Raikkonen.
Mercedes appeared to be quicker in the first sector, but both Lewis Hamilton's and Valtteri Bottas's laps fell away thereafter.
Bottas was Ferrari's closest challenger in third, 0.670s off the pace, with Hamilton a few thousandths further back in fourth.
It was a scrappy session for Mercedes as both drivers struggled to get their Pirelli tyres into the right operating window, their quickest times coming several laps into the run.
Max Verstappen got the better of Red Bull team-mate Daniel Ricciardo and ended the day fifth fastest, just over three tenths clear of the Australian.
However Verstappen's session ended 20 minutes early when he parked at the side of the track and reported he was "out of power".
The close battle in the midfield looks set to continue with only half-a-second separating Williams' Felipe Massa in seventh and Renault's Jolyon Palmer in 13th.
Between them was Nico Hulkenberg, Kevin Magnussen, Sergio Perez, Esteban Ocon and Fernando Alonso.
Romain Grosjean, whose Haas team tried a different brake supplier in Friday practice, complained of understeer throughout as he finished 14th.
Toro Rosso had a tough session with Carlos Sainz Jr and home favourite Daniil Kvyat 15th and 17th respectively after their runs on the ultra-softs.
Stoffel Vandoorne, who sighed "incredible" as one of the Force Indias breezed by, ended up 16th, just under four tenths adrift of Alonso.
The McLaren driver is set to start Sunday's race from the back of the grid after the team changed the entire Honda engine ahead of FP2 following more problems on Friday morning, earning a 15-place grid penalty.
Lance Stroll was 19th, 1.5s slower than team-mate Massa, but he was the only driver who did not run the ultra-soft tyre.
PRACTICE TWO TIMES: