Championship leader Lewis Hamilton clocked the third fastest time in Singapore as Daniel Ricciardo completed a practice double on an impressive day for Red Bull.
Ricciardo set the fastest lap in opening practice before he went even quicker under the lights of the Marina Bay circuit to finish half-a-second clear of his Red Bull team-mate Max Verstappen with a record-breaking time of one minute and 40.852 seconds.
Hamilton, who holds a three-point advantage in the title race, was next in the order and the only other driver within one second of Ricciardo and his rampant Red Bull.
In contrast, Hamilton's title rival Sebastian Vettel was just 11th, but his result is somewhat skewed given that he failed to post a fast lap on the ultrasoft tyre, the quickest of the three compounds available.
Vettel went quicker than any other driver in the opening sector of what should have been his best lap, only to be blocked by the Sauber of Marcus Ericsson before abandoning his run.
To cap a scrappy evening, the four-time champion then thudded the wall on the exit of turn 10, dislodging an advertising board, but escaped the incident without any significant damage to his car.
But with Vettel's team-mate Kimi Raikkonen only ninth in the standings, there will be some concern in the Ferrari camp on Friday night with the slow-speed nature of this 3.2-mile street circuit expected to have played to their strengths.
This weekend's race could prove to be the only course of the remaining seven grands prix where Ferrari will hold the advantage over Hamilton and his Mercedes team.
Hamilton, who is in charge of the title race for the first time this season following his triumph at the Italian Grand Prix a fortnight ago, will feel somewhat relieved to have seen Vettel behind him with Mercedes braced for a difficult weekend.
The 32-year-old Englishman has won in Singapore on two occasions, but he has struggled in recent years, failing to get to the finish in 2015 before he ended a distant third to rival Nico Rosberg in last season's race.
But aside from the dominant Red Bulls, Hamilton was half-a-second clear of his fourth-placed Mercedes team-mate Valtteri Bottas, and seemingly in with a chance of retaining his championship lead over Vettel.
"We were obviously close with the field today and we have still got some improvements to make with the car," Hamilton said. "Red Bull seem like they're very strong and they're thereabouts with Ferrari, so we've got some work to do. But nothing is out of reach."
Hamilton has been on pole position at both races since the summer break, and qualifying is crucial in Singapore with overtaking virtually impossible. Seven of the last nine pole-sitters have gone on to win.
Hamilton also revealed that he will be adapting his diet after watching the pro-vegan Netflix film 'What the Health'. "I'm on a mission to go vegan people," he informed his millions of Instagram followers. "Animal cruelty, global warming and our personal health is at stake."
Elsewhere, Nico Hulkenberg was fifth for Renault, while McLaren's Stoffel Vandoorne finished sixth ahead of his team-mate Fernando Alonso.
The McLaren pair will be powered by Renault next year after the British team formally announced their divorce from Honda. Honda will instead move to Red Bull's junior team Toro Rosso in 2018 with Carlos Sainz to partner Hulkenberg at Renault.
Renault's move to appoint Sainz leaves British driver Jolyon Palmer in the lurch. Palmer, 26, has failed to score a single point this year, and was only 14th on Friday, 1.4 sec slower than Hulkenberg in the sister Renault.