Lewis Hamilton was in superlative form to set the pace in second practice at the Russian Grand Prix.
Hamilton's Mercedes team-mate and title rival Nico Rosberg was fourth fastest, 0.912 seconds adrift.
McLaren's Kevin Magnussen was second fastest, 0.864secs off Hamilton, with Ferrari's Fernando Alonso third, a further 0.01secs adrift of the Dane.
The weekend is taking place just days after the accident suffered by Marussia driver Jules Bianchi in Japan.
The Frenchman's team have decided to run only one car in honour of Bianchi, who is in hospital in Japan in a critical condition after suffering severe head injuries in the crash on a very wet Suzuka track on Sunday.
World champion Sebastian Vettel said: "Does getting back in the car help us after what's happened? It does and it doesn't. It helps to get your head elsewhere and focus on the day job - looking after the best possible set-up and comparing the tyres and learning the new track; it keeps you occupied.
"But on the other hand it's only been a couple of days, so it's quite fresh and difficult."
The single Marussia car of Max Chilton was 20th fastest, between the two cars of back-of-the-grid rivals Caterham, for whom Marcus Ericsson was 19th and Kamui Kobayashi 21st.
Williams's Valtteri Bottas was fifth, split from team-mate Felipe Massa in seventh by McLaren's Jenson Button.
At the front, Hamilton comes to Russia on the back of three straight wins, including in Japan last weekend, when he became the first Mercedes driver to make a pass stick on his rival in a wheel-to-wheel battle all season.
Rosberg has offered no excuses for his performance, saying that Hamilton coped better with the loose rear end in difficult conditions in Japan.
But he added: "I believe and know that if I do a good job here, I'll win on Sunday. I'm not in the past. I'm here."
Rosberg appeared to have an edge on Hamilton initially in practice - he was quickest in the first session and was quicker by 0.242secs in the early part of the session, when the drivers were running on the harder 'medium' tyre.
Then, Hamilton was struggling with his inside wheel locking as he braked into Turn 13, at the end of the long back straight.
But Hamilton pulled off some stunning performances on the runs on the faster 'soft' tyre, putting in two laps more than 0.6secs quicker than Rosberg.
Rosberg ran wide at one corner and was complaining that he was not happy with the car.
And on the longer runs at the end of the session, when the teams were simulating race performance, Hamilton appeared to be in a league of his own, an average of nearly half a second a lap quicker than of Rosberg. Bottas also looked impressively fast on the race runs.
Behind Massa on headline times, Toro Rosso's Daniil Kvyat was eighth ahead of the Red Bull of Sebastian Vettel and the Russian's team-mate Jean-Eric Vergne was 10th.
The second Ferrari of Kimi Raikkonen was one second off Alonso, who unusually set his fastest time at the end of a multi-lap run on the soft tyre.
Force India's Nico Hulkenberg was 12th, ahead of Red Bull's Daniel Ricciardo, who stopped with seven minutes of the session remaining with a power unit failure.
Red Bull team principal Christian Horner said the team were slower than they expected to be.
"We appear to be out of the window we normally are in," Horner said. "We'd expect to be up with McLaren, Williams and Ferrari. The drivers are not saying there's anything particularly wrong with the car, but it doesn't seem quite quick enough."
The Sochi track carries a strong resemblance to the now defunct Valencia street circuit and Hamilton and Rosberg were among the many drivers who ran wide, exploring the limits at the plethora of right-handed corners.
Turn 13 - into which drivers have to brake while going through a left-hand kink at the end of the long back straights - was proving particularly challenging, with a number of drivers running wide.