Championship leader Lewis Hamilton survived a dramatic spin in the final minutes as he continued his domination of practice at the inaugural Russian Grand Prix on Saturday.
The 29-year-old Briton, fastest on Friday, clocked the best time again for Mercedes with some ease in the final session before making a mistake at the penultimate corner and spinning to a halt in the run-off area at Turn 17.
His tyres were wrecked and his session ended, with five minutes remaining, but by then he had set such a scorching pace he was clearly favourite to take pole position in qualifying later on Saturday.
Hamilton's Mercedes team-mate Nico Rosberg of Germany, who is 10 points behind him with four races remaining, battled through the session to take second place, 0.290 seconds behind.
"It was a tremendous lap," said Mercedes team boss Toto Wolff. "He seems to extract the maximum out of the car at the moment.
"Somehow, Lewis seems to nail it from the first lap, but Nico seems to struggle a bit more - but this is just practice."
Finn Valtteri Bottas of Williams was third quickest, three-tenths off Hamilton's pace, ahead of Australian Daniel Ricciardo in the leading Red Bull, who was more than a second slower than the fastest lap.
Brazilian Felipe Massa of Williams was fifth ahead of Russian rookie Daniil Kvyat, who leaves Toro Rosso for Red Bull next year, and Finn Kimi Raikkonen who was seventh in the leading Ferrari.
Spaniard Fernando Alonso was eighth in the second Ferrari, Frenchman Jean-Eric Vergne ninth in the second Toro Rosso and German four-time champion Sebastian Vettel, who leaves Red Bull at the end of the season, was 10th.
After showing strong pace and performance on Friday, Briton Jenson Button of McLaren was down in 13th while Danish team-mate Kevin Magnussen suffered a mechanical failure which led to a red flag, after 15 minutes, as he spun on track in the second McLaren.
Five days after Jules Bianchi's life-threatening accident at the Japanese Grand Prix, teams held meetings to discuss revised safety measures for the future before the session began, following pledges made by the organising body the International Motoring Federation (FIA) on Friday to learn lessons and apply them.