In the final hour-long practice session, and as dusk settled over the Marina Bay Street Circuit, Vettel improved on his quickest lap from Friday's two 90-minute runs.
Vettel's advantage, however, was slashed, with Lotus' Romain Grosjean emerging as second fastest, the Frenchman stepping up to the plate as requested by team principal Eric Boullier with Kimi Raikkonen on his way back to Ferrari.
In the closing stages, and with the supersoft tyres strapped on to the cars for the final 10 minutes after the majority of the session was run on the medium Pirelli compound, Vettel posted a time of one minute 44.173 seconds, just 0.076secs faster than his best of Friday.
Grosjean managed to finish within two tenths of a second of reigning three-times champion Vettel, who currently has a 53-point lead over his nearest rival in Ferrari's Fernando Alonso in his quest for a fourth successive title.
Behind Grosjean was Mercedes' Nico Rosberg, with team-mate Lewis Hamilton fifth on the timesheet, the duo sandwiching Red Bull's Mark Webber.
Rosberg was just over half a second down, with Webber and Hamilton in close attendance, around three quarters of a second back, and clearly still needing to improve to have any chance of pole.
Alonso was a second down and on his own in sixth as Sergio Perez in his McLaren, under pressure to perform this weekend with his job on the line, was seventh and 1.327secs adrift.
Sauber's Nico Hulkenberg, Jenson Button in his McLaren and Ferrari's Felipe Massa completed the top 10, the latter at least only 0.7secs behind team-mate Alonso following a miserable Friday in the car.
Raikkonen, 88 points behind Vettel and with his title chances hanging by a thread, was a lowly 12th, two seconds off the pace.
Force India's Paul Di Resta could only manage 16th in what appeared to seemingly be another tricky session for the Scot, who spun at one point, although he at least finished ahead of team-mate Adrian Sutil who was down in 18th.
At the rear of the field and nearly six seconds down was Marussia's Max Chilton, with team-mate Jules Bianchi 0.8secs ahead of him.
Earlier in the session, on the medium tyres, Webber set the quickest time with a lap of 1:46.220, a fraction of a second ahead of Vettel, with Hamilton third quickest and a quarter of a second back.