Renault's Fernando Alonso snatched the top spot from Felipe Massa in the closing seconds of Friday afternoon practice for the Brazilian Grand Prix, while the Ferrari driver's title rival Lewis Hamilton managed only ninth position.
Jarno Trulli completed the top three for Toyota, ahead of Massa's teammate Kimi Raikkonen.
While Massa was a factor at the front throughout, Hamilton spent most of the afternoon around the foot of the top ten - lapping over half a second slower than his practice one pace and regularly locking wheels in the middle sector. He also failed to gain significant ground on the softer tyres, although the Briton switched compounds just as one of the light rain showers really took effect.
Massa hit the front for the first time after 12 minutes, but was only on top for a minute before his time was beaten by Trulli.
Both were then usurped by Nico Rosberg four minutes later as the Williams driver became one of the first to evaluate the soft tyres, with Trulli then following his example to reclaim first position shortly afterwards.
Ferrari preferred to stay on hard tyres for the time being, and a fresh set of these was sufficient to put Massa back in front with a 1:12.569 after half an hour. He then improved by a further 0.216 seconds when he tried the soft tyres on his next run.
The times subsequently stayed relatively static for the rest of the afternoon, as the ever-present drizzle increased and led to a number of wild slides as drivers scrambled for grip in the cold conditions.
Both Toyota drivers had quick spins, Toro Rosso's Sebastien Bourdais had a number of excursions under braking for the Senna S, and Mark Webber managed to restrict his Red Bull to a high-speed half-spin after it snapped sideways under braking for the Descida do Lago.
By the closing minutes, the track had dried enough for times to start improving, and with 90 seconds remaining Alonso vaulted from a lowly 18th place to the top of the timing screens using soft tyres, with his teammate Nelson Piquet jumping from last to seventh at the same moment.
That pushed Massa and Trulli back to second and third, ahead of Raikkonen, Red Bull's Mark Webber and Toro Rosso's Sebastian Vettel.
Rosberg fell to eighth at the end of the session, as Hamilton locked his brakes in the middle sector yet again on his final flying lap and ended the day ninth, ahead of Kazuki Nakajima (Williams). The Briton's McLaren teammate Heikki Kovalainen managed only 15th place.
Pos Driver Car Time Laps 1. Alonso Renault (B) 1:12.296 43 2. Massa Ferrari (B) 1:12.353 + 0.057 41 3. Trulli Toyota (B) 1:12.435 + 0.139 44 4. Raikkonen Ferrari (B) 1:12.600 + 0.304 32 5. Webber Red Bull-Renault (B) 1:12.650 + 0.354 45 6. Vettel Toro Rosso-Ferrari (B) 1:12.687 + 0.391 47 7. Piquet Renault (B) 1:12.703 + 0.407 44 8. Rosberg Williams-Toyota (B) 1:12.761 + 0.465 42 9. Hamilton McLaren-Mercedes (B) 1:12.827 + 0.531 33 10. Nakajima Williams-Toyota (B) 1:12.886 + 0.590 42 11. Coulthard Red Bull-Renault (B) 1:12.896 + 0.600 38 12. Kubica BMW Sauber (B) 1:12.971 + 0.675 48 13. Heidfeld BMW Sauber (B) 1:13.038 + 0.742 49 14. Glock Toyota (B) 1:13.041 + 0.745 39 15. Kovalainen McLaren-Mercedes (B) 1:13.213 + 0.917 37 16. Barrichello Honda (B) 1:13.221 + 0.925 39 17. Bourdais Toro Rosso-Ferrari (B) 1:13.273 + 0.977 41 18. Button Honda (B) 1:13.341 + 1.045 49 19. Sutil Force India-Ferrari (B) 1:13.428 + 1.132 32 20. Fisichella Force India-Ferrari (B) 1:13.691 + 1.395 33 All timing unofficial