Red Bull's title challenger Sebastian Vettel was quickest in second free practice for Sunday's Singapore Grand Prix.
Vettel has a distant chance of claiming the title, trailing leader Jenson Button by 26 points with 40 available for the rest of the season.
Renault driver Fernando Alonso put in a scorching lap late on to go second, in Renault's first race since Flavio Briatore and Pat Symonds left the team after the race-fix scandal.
Button was fifth fastest in his Brawn, with team mate and closest title rival Rubens Barrichello in 11th.
The only other driver with a chance of the title Mark Webber was sixth fastest, despite the fact he had to sit out the second half of the session after spinning his Red Bull at the first corner. The session was held up as a result of his off.
In the earlier session, Barrichello had set the pace but the session was also held up after an off by Renault's Romain Grosjean. His spin was at turn 17, the same corner where Renault asked Nelson Piquet Jr to deliberately crash at last year.
Times taken from second free practice session:
1. Vettel Red Bull-Renault 1:48.650 2. Alonso Renault + 0.2743. Kovalainen McLaren-Mercedes + 0.302 4. Heidfeld BMW-Sauber + 0.4485. Button Brawn-Mercedes + 0.661 6. Webber Red Bull-Renault + 0.667 7. Rosberg Williams-Toyota + 0.683 8. Glock Toyota + 0.6929. Hamilton McLaren-Mercedes + 0.708 10. Kubica BMW-Sauber + 0.95911. Barrichello Brawn-Mercedes + 0.966 12. Sutil Force India-Mercedes + 1.060 13. Trulli Toyota + 1.145 14. Raikkonen Ferrari + 1.29115. Nakajima Williams-Toyota + 1.373 16. Fisichella Ferrari + 1.603 17. Buemi Toro Rosso-Ferrari + 1.877 18. Liuzzi Force India-Mercedes + 1.955 19. Grosjean Renault + 2.322 20. Alguersuari Toro Rosso-Ferrari + 2.773
All timings unofficial