Sebastian Vettel shattered the Marina Bay lap record as he bounced back from his Friday brush with the wall to top the Practice Three timesheet.
Vettel produced a stunning 1:38.054 on hypersoft tyres to beat the record Kimi Raikkonen had set in Practice Two by over six tenths of a second.
Raikkonen was 0.362s slower than his team-mate in second, with championship leader Lewis Hamilton half a second behind title rival in third and just ahead of Valtteri Bottas.
"I'm not convinced the Mercedes is at the same level of the Ferrari," Sky F1's Anthony Davidson said on commentary.
"Hamilton has been digging deep all season but he's going to have to really find something special in qualifying."
From his opening lap, Vettel had showed no signs of his confidence being dented by his Friday bang as he got within millimetres of the wall on the exit of Turn 21 on his opening lap.
With the evening conditions not truly representative of qualifying and race conditions, Red Bull opted to focus on long-run simulations until the closing minutes of the session.
But neither Daniel Ricciardo nor Max Verstappen could get close to Ferrari or Mercedes, having to settle for fifth and sixth respectively and over a second slower than Vettel's best time.
Verstappen was also heard venting his frustrations with the Renault power unit over team radio once again.
"The product in the back of this car is not working like I want it to," he said when asked to give more feedback.
Romain Grosjean was seventh for Haas while Esteban Ocon took eighth and Sergio Perez ninth for Force India, who are running a new aero package this weekend.
For the second consecutive session, Fernando Alonso got his McLaren into the top 10, just ahead of Nico Hulkenberg's Renault.