Lewis Hamilton, who won the Italian Grand Prix two weeks ago, was second for Mclaren – half a tenth behind – with team-mate Jenson Button a further eight tenths back, while Championship leader Fernando Alonso finished in fourth.
In the opening 30 minutes, spectators watched as drivers battled around the damp circuit, with most drivers opting for the intermediate tyres.
As most teams elected to only complete an installation lap, the most notable moment early in the session came when Michael Schumacher misjudged a braking zone and almost clattered into the back of his Mercedes team-mate Nico Rosberg.
Halfway through the session as night fell over the spectacular backdrop of the skyscrapers of Singapore, Sauber’s Kamui Kobayashi signalled the start of competitive lap times, setting the quickest time on dry tyres.
As lap times were traded throughout the remainder of the session, it was Red Bull’s Vettel and Mclaren’s Hamilton who set the pace with a large distance between them and the rest of the field.
1. Sebastian Vettel (Ger) Red Bull 1:50.566
2. Lewis Hamilton (Gbr) McLaren (+0.049)
3. Jenson Button (Gbr) McLaren (+0.893)
4. Fernando Alonso (Spa) Ferrari (+0.959)
5. Pastor Maldonado (Ven) Williams (+1.010)
6. Mark Webber (Aus) Red Bull (+1.089)
7. Nico Hulkenberg (Ger) Force India (+1.092)
8. Paul di Resta (Gbr) Force India (+1.377)
9. Daniel Ricciardo (Aus) Scuderia Toro Rosso (+1.709)
10. Sergio Perez (Mex) Sauber-Ferrari (+1.730)
11. Bruno Senna (Bra) Williams (+2.063)
12. Kimi Raikkonen (Fin) Lotus F1 Team (+2.150)
13. Kamui Kobayashi (Jpn) Sauber-Ferrari (+2.273)
14. Michael Schumacher (Ger) Mercedes GP (+2.420)
15. Romain Grosjean (Fra) Lotus F1 Team (+2.462)
16. Felipe Massa (Bra) Ferrari (+2.514)
17. Jean-Eric Vergne (Fra) Scuderia Toro Rosso (+2.623)
18. Nico Rosberg (Ger) Mercedes GP (+2.661)
19. Timo Glock (Ger) Marussia (+4.342)
20. Heikki Kovalainen (Fin) Caterham (+4.525)
21. Charles Pic (Fra) Marussia (+4.769)
22. Vitaly Petrov (Rus) Caterham (+5.194)
23. Pedro de la Rosa (Spa) HRT-F1 (+6.090)
24. Ma Qing Hua (Chi) HRT-F1 (+7.487)