Mark Webber was quickest for Red Bull in the opening Brazilian Grand Prix practice session at a dry and sunny Interlagos.
A 1m13.811s lap for Webber heading into the final quarter of an hour saw him depose the two McLarens, with Jenson Button and Lewis Hamilton second and third ahead of Sebastian Vettel in the second Red Bull. All four were within 0.214 seconds.
The McLarens and Red Bulls had dominated the top of the standings once the serious running began after the first half hour, with Hamilton and Button up front for a quarter of an hour before Vettel took a turn in first place.
Button usurped the champion around the one-hour mark, with Hamilton coming in behind him to briefly form a McLaren one-two, before Webber set what proved to be the morning's fastest time.
The Ferraris completed the top six, with Felipe Massa ahead of Fernando Alonso - who parked with an engine failure four minutes from the end.
Michael Schumacher and Nico Rosberg's Mercedes took seventh and 10th, sandwiching the Force Indias of Nico Hulkenberg and Paul di Resta.
Hulkenberg was just one member of a large test and reserve driver contingent in action. Romain Grosjean was 12th for Renault despite stopping in the pit exit with clutch trouble after an hour. Toro Rosso's Jean-Eric Vergne took 18th, Luiz Razia was 20th on his return to Lotus duty, and Jan Charouz's grand prix weekend debut saw him slowest but within 0.6s of HRT team-mate Daniel Ricciardo.
There were no significant off-track incidents in the session bar a handful of trips over the run-off area and a swift spin for Sauber's Kamui Kobayashi.
Pos Driver Team Time Laps 1. Mark Webber Red Bull-Renault 1m13.811s 26 2. Jenson Button McLaren-Mercedes 1m13.825s + 0.014 25 3. Lewis Hamilton McLaren-Mercedes 1m13.961s + 0.150 20 4. Sebastian Vettel Red Bull-Renault 1m14.025s + 0.214 28 5. Felipe Massa Ferrari 1m14.507s + 0.696 34 6. Fernando Alonso Ferrari 1m14.541s + 0.730 26 7. Michael Schumacher Mercedes 1m15.162s + 1.351 28 8. Nico Hulkenberg Force India-Mercedes 1m15.178s + 1.367 28 9. Paul di Resta Force India-Mercedes 1m15.241s + 1.430 31 10. Nico Rosberg Mercedes 1m15.321s + 1.510 29 11. Jaime Alguersuari Toro Rosso-Ferrari 1m15.468s + 1.657 29 12. Romain Grosjean Renault 1m15.547s + 1.736 18 13. Rubens Barrichello Williams-Cosworth 1m15.663s + 1.852 27 14. Bruno Senna Renault 1m15.732s + 1.921 32 15. Kamui Kobayashi Sauber-Ferrari 1m15.747s + 1.936 31 16. Pastor Maldonado Williams-Cosworth 1m15.836s + 2.025 27 17. Sergio Perez Sauber-Ferrari 1m15.979s + 2.168 35 18. Jean-Eric Vergne Toro Rosso-Ferrari 1m16.052s + 2.241 33 19. Heikki Kovalainen Lotus-Renault 1m16.514s + 2.703 33 20. Luiz Razia Lotus-Renault 1m17.595s + 3.784 31 21. Timo Glock Virgin-Cosworth 1m18.140s + 4.329 29 22. Jerome D'Ambrosio Virgin-Cosworth 1m18.653s + 4.842 29 23. Daniel Ricciardo HRT-Cosworth 1m18.952s + 5.141 33 24. Jan Charouz HRT-Cosworth 1m19.577s + 5.766 37 All Timing Unofficial