Mark Webber kept Red Bull on top of the times in final practice for the Singapore Grand Prix, as team-mate Sebastian Vettel had to settle for third place after finding traffic.
Webber's time of 1m46.081s put him just 0.027 seconds ahead of McLaren's Jenson Button, who bounced back following a difficult Friday.
Vettel, favourite for another pole position, had a low-key session and finished in third, over two tenths of a second behind Webber. The German, however, was hit by traffic during his best laps.
Fernando Alonso, a two-time winner in Singapore, put his Ferrari in fourth place, with Lewis Hamilton down in fifth place in the second McLaren. The Briton, however, was nearly a full second off the pace after damaging his car's floor when going over the kerbs during the final moments of the session.
Virgin's Jerome D'Ambrosio set the first time of the session after some 12 minutes, while all the other drivers settled for installation laps in the opening part of final practice.
Kamui Kobayashi moved to the top of the times some two minutes later, with the rest of the field starting to complete timed laps.
Button was the first of the frontrunners to complete a full lap, the Briton stopping the clock at 1m50.707s, the McLaren driver improving by over a second as he continued with his run. Button continued to stretch his gap for a few laps, posting a 1m48.412s that left him over 1.5 seconds clear of the field at the 30-minute mark.
Vettel shot to the top of the times with less than half the session to go, the world champion posting a 1m47.737s with the soft tyre compound. Alonso moved to second with a lap very much on the limit, the Spaniard having already survived a scare during his previous lap.
Vettel improved even further to stop the clock at 1m47.064s, with Michael Schumacher outpacing Alonso to jump up to second place with 20 minutes left.
Nico Rosberg was the first of the frontrunners to try the supersoft rubber, the German posting the second quickest time with around 12 minutes to go.
Despite brushing the wall, Alonso went quickest during his first run with the softer rubber, the Spaniard bettering Vettel's time by over six tenths of a second. Button was next to complete his super soft-tyre run, posting a 1m46.108s that put him on top.
The Briton was soon relegated, however, when Webber went quicker by 0.027s. Team-mate Vettel had to settle for third position in his first run with super softs after finding traffic during his lap. The world champion went for another run with the same set of tyres but decided to abort it in the end.
Pos Driver Team Time Laps
1. Mark Webber Red Bull-Renault 1m46.081s 15
2. Jenson Button McLaren-Mercedes 1m46.108s + 0.027 17
3. Sebastian Vettel Red Bull-Renault 1m46.345s + 0.264 14
4. Fernando Alonso Ferrari 1m46.396s + 0.315 14
5. Lewis Hamilton McLaren-Mercedes 1m46.936s + 0.855 20
6. Nico Rosberg Mercedes 1m47.831s + 1.750 14
7. Michael Schumacher Mercedes 1m47.837s + 1.756 12
8. Felipe Massa Ferrari 1m48.711s + 2.630 12
9. Kamui Kobayashi Sauber-Ferrari 1m49.057s + 2.976 15
10. Adrian Sutil Force India-Mercedes 1m49.304s + 3.223 16
11. Sergio Perez Sauber-Ferrari 1m49.583s + 3.502 17
12. Sebastien Buemi Toro Rosso-Ferrari 1m49.679s + 3.598 18
13. Paul di Resta Force India-Mercedes 1m49.816s + 3.735 18
14. Pastor Maldonado Williams-Cosworth 1m49.851s + 3.770 17
15. Rubens Barrichello Williams-Cosworth 1m50.189s + 4.108 15
16. Vitaly Petrov Renault 1m50.229s + 4.148 15
17. Bruno Senna Renault 1m50.523s + 4.442 14
18. Jaime Alguersuari Toro Rosso-Ferrari 1m50.547s + 4.466 17
19. Heikki Kovalainen Lotus-Renault 1m52.510s + 6.429 17
20. Jerome D'Ambrosio Virgin-Cosworth 1m52.697s + 6.616 19
21. Daniel Ricciardo HRT-Cosworth 1m53.728s + 7.647 17
22. Jarno Trulli Lotus-Renault 1m53.823s + 7.742 18
23. Timo Glock Virgin-Cosworth 1m53.829s + 7.748 16
24. Tonio Liuzzi HRT-Cosworth 1m55.203s + 9.122 17
All Timing Unofficial