Spaniard Carlos Sainz led team mate Charles Leclerc in a Ferrari one-two at the end of Friday's Formula One practice for the Singapore Grand Prix.
The 28-year-old lapped the 5km Marina Bay track in one minute, 42.587 seconds to end the day 0.208 seconds quicker than Leclerc.
George Russell continued to show promise for Mercedes, after team mate Lewis Hamilton went quickest in Friday's opening session, with the third-fastest time, 0.324 seconds adrift.
That put the Briton less than a tenth of a second clear of birthday boy Max Verstappen, who was second during the first hour of practice but spent much of the floodlit second session in the garage, only coming out in the closing minutes to set the fourth quickest time.
Verstappen goes into Sunday's floodlit Singapore spectacular, back on the calendar after a two-year COVID-19 induced absence, with his first shot at wrapping up a second successive title.
The Red Bull racer, who turned 25 on Friday, is 116 points clear of Leclerc and 125 ahead of team mate Sergio Perez in the overall standings.
Sunday's race will offer him his first chance of clinching a second successive title with the Dutchman needing to score at least 22 points more than Leclerc and 13 points more than Perez to get the job done.
Hamilton, whose effort in Friday's opening session put him at the top of the timesheets for the first time this season, ended the day fifth.
Esteban Ocon was sixth for Alpine ahead of Alfa Romeo's Valtteri Bottas and the other Alpine of Spaniard Fernando Alonso.
Perez was only ninth in the other Red Bull, also logging low mileage, with Canadian Lance Stroll rounding out the top-10 for Aston Martin.
Thai racer Alexander Albon, who underwent appendicitis surgery and suffered respiratory failure from post-operative anaesthetic complications earlier this month, was again 16th fastest for Williams.
He completed a total of 45 gruelling laps of the punishing Marina Bay track over both sessions.
Pierre Gasly endured a fiery end to his session with his AlphaTauri spewing flames from its airbox as it was wheeled back into the garage.
In the first session, Hamilton lapped the 5km Marina Bay circuit in one minute 43.033 seconds, with Verstappen, celebrating his 25th birthday, 0.084 seconds adrift in his Red Bull.
Monegasque Charles Leclerc (24) in his Ferrari was third.
Mercedes, meanwhile, are also hunting for their first win.
The tight twists of the Marina Bay street track are suited to their car and could be enough to allow Hamilton, who has never ended a season without a win, to chalk up a season-first triumph or team mate George Russell to take his first career win.
Perez was fourth for Red Bull with Russell, surviving a spin and a nudge into the barriers, fifth.
Carlos Sainz was sixth for Ferrari ahead of Alpine's Esteban Ocon.
Canadian Lance Stroll, who brought out the red flags when he ground to a halt, was eighth for Aston Martin.
AlphaTauri's Pierre Gasly and Fernando Alonso in his Alpine rounded out the top-10.
Thai racer Alexander Albon, who underwent appendicitis surgery and suffered respiratory failure from post-operative anaesthetic complications earlier this month, was 16th fastest for Williams.
He completed 20 laps, the same as session topper Hamilton, of the physically-demanding Marina Bay layout.
The Singapore Grand Prix, which takes place at night against a backdrop of glittering skyscrapers and has established itself as one of the sport's most popular races, is returning to the calendar for the first time since 2019 this season.
The race was absent during the last two years due to the COVID-19 pandemic.
