Championship leader Nico Rosberg lapped more than a second quicker than last year's pole position time as Mercedes dominated Bahrain Grand Prix practice on Friday.
The German, who is chasing his fifth victory in a row after winning Formula One's season-opener in Australia and the last three races of 2015, led both sessions with his triple champion team mate Lewis Hamilton second.
Rosberg's best lap of one minute 31.001 seconds, in the floodlit evening session at the Sakhir circuit compared to Hamilton's 2015 pole of 1.32.671.
Hamilton, winner for the past two years in Bahrain, was the only other driver to lap below the 1:32 mark with a best effort of 1:31.242. McLaren's Jenson Button produced a third best time of 1:32.281 on the super-soft tyres.
Ferrari's Kimi Raikkonen had been third fastest in the afternoon practice, a hefty 1.834 off Rosberg's pace on the same soft tyres as the Mercedes pair.
The Red Bulls of Australian Daniel Ricciardo and Russian Daniil Kvyat were fourth and fifth in that same session but Toro Rosso's Max Verstappen and Raikkonen filled those places in the evening.
Ferrari's Sebastian Vettel, third in Australia, was sixth but pulled off the track and stopped late in the second session with a loose wheel.
"The rear-left corner (wheel) is not tight. The nut is not on, that was the problem," the four-times world champion said over the team radio. Belgian Stoffel Vandoorne got to grips with the McLaren ahead of his Formula One race debut as stand-in for the injured Fernando Alonso and was 18th on the 22-driver timesheet in the first session.
The rookie moved up to 11th after another 30 laps in the second practice. Vandoorne, who flew in from Japan where he is racing in the Super Formula series this season, had not previously driven the 2016 McLaren.
Spaniard Alonso was ruled out on Thursday, after failing to pass a medical following his big crash in Australia, and could also miss the following race in China on April 17.
Las Vegas on line
Las Vegas could host a second U.S. race on the Formula One calendar in a few years' time but a deal has yet to be agreed, the sport's commercial supremo Bernie Ecclestone said on Friday.
"I am going to be talking to them (Las Vegas promoters) in another 10 minutes' (time)," Ecclestone told reporters during practice at the Bahrain Grand Prix, when asked about negotiations.
"It's possible that there could be an event there," added the 85-year-old Briton.
Asked when the race in the desert resort might happen, he replied: "In a couple of years I suppose. We'd keep Austin and have another race."
The Formula One calendar currently has a record 21 races, with Azerbaijan's Baku street circuit due to debut in June, and Ecclestone has said that is probably the limit.
Las Vegas hosted two Formula One grands prix in 1981 and 1982, with the track laid out in the parking lot of the Caesars Palace hotel and casino.
The purpose-built Circuit of the Americas in Austin, Texas, is the only U.S. race on the current calendar that includes Montreal and Mexico City as the two other venues in North America.
Formula One has long sought a second race in the United States, a key market for sponsors and car manufacturers, with New Jersey listed on the provisional 2014 calendar for an event that never happened due to funding problems.