Championship leader Sebastian Vettel topped the times again for Ferrari in Friday's hotly-contested second free practice ahead of this weekend's Bahrain Grand Prix.
Having lapped quickest to top the opening session in very hot conditions, the four-time champion remained the man to beat in cooler temperatures in the floodlit session at the Bahrain International Circuit where the sport's former commercial supremo Bernie Ecclestone made his first appearance at a race since new owners Liberty Media took over the sport.
Vettel clocked an early best lap in one minute and 31.310 seconds during a run on super-soft tyres, a time that left him 0.041 seconds ahead of nearest rival Valtteri Bottas of Mercedes.
The Finn, who replaced retired 2016 champion Nico Rosberg in the champion team, was second 0.025 seconds clear of third placed Daniel Ricciardo of Red bull, the front three all separated by just 0.066 seconds.
Kimi Raikkonen, the 2007 champion, was fourth quickest in the second Ferrari ahead of Mercedes' three-time champion Lewis Hamilton, who shares the title race lead with Vettel after two races so far this season.
The Briton was unable to clock a truly competitive lap on his super-soft runs and had to take evasive action when he came upon Nico Hulkenberg idling on the racing line in Turn One.
"These drivers are so dangerous, man," said Hamilton, on his team radio, as he backed off and aborted his lap.
The incident was reported to the stewards and was due for investigation post-session. Vettel also had problems mid-way through the session when his Ferrari lost power.
"Complete shutdown," he told his team as he nursed his car back to the pits.
The German rejoined for the long race-simulation runs in the final part of the session. Verstappen's efforts were also thwarted by problems when he ran over the 't-wing' that flew off Bottas's Mercedes and damaged the floor of his Red Bull car.
The session was run in track temperatures of 35 degrees Celsius and air temperatures of 34 degrees, some 14 degrees cooler than it had been in the opening session.