Nico Rosberg kept Mercedes at the top of the timesheets in a second wet Friday practice session for the Brazilian Grand Prix.
Heavy rain before the start of the session left the Interlagos track saturated, contributing to a general dearth of action that prevailed until a frantic final 10 minutes.
The initial situation was exacerbated as the rain abated and conditions entered the uncertain window between wets and intermediates, with those who did venture out being warned about overheating problems on their wets.
Such circumstances meant that only six drivers set a time over the opening half hour, while seven drivers - among them Sebastian Vettel, Fernando Alonso and Lewis Hamilton - still had to set a time at the hour mark.
For a long while Rosberg's early 1m28.873s was therefore good enough for top spot, but Alonso helped breathe life into the session when he headed out on intermediates 20 minutes from the end and immediately went third.
That provided the encouragement for Felipe Massa, Vettel, Hamilton and the rest of the pack to also emerge on intermediates, with times tumbling as a result.
Sebastian Vettel kicked off the surge when he demoted Rosberg with a 1m27.993s, at the time seven tenths clear of the field.
He extended that advantage further, while behind him Webber also improved to move into second and complete a Red Bull one-two two minutes from the end.
Rosberg still had time to respond however, and duly disrupted the Red Bull party by reclaiming top spot with a 1m27.306s.
That was more than 0.8s clear of team-mate Hamilton, who clinched fifth on his final flyer. The Briton had earlier spun in the treacherous conditions.
Heikki Kovalainen's Lotus split Hamilton and the two Red Bulls.
Jean-Eric Vergne put his Toro Rosso sixth, fractions ahead of Ferrari's departing Felipe Massa and Sauber's Nico Hulkenberg.
Daniel Ricciardo and Romain Grosjean completed the top 10, ahead of Alonso, Esteban Gutierrez and Paul di Resta, back in the Force India after James Calado took over driving duties for first practice.
Pos Driver Team Time Gap Laps 1. Nico Rosberg Mercedes 1m27.306s 12 2. Sebastian Vettel Red Bull-Renault 1m27.531s +0.225s 10 3. Mark Webber Red Bull-Renault 1m27.592s +0.286s 18 4. Heikki Kovalainen Lotus-Renault 1m28.129s +0.823s 13 5. Lewis Hamilton Mercedes 1m28.147s +0.841s 9 6. Jean-Eric Vergne Toro Rosso-Ferrari 1m28.405s +1.099s 11 7. Felipe Massa Ferrari 1m28.540s +1.234s 9 8. Nico Hulkenberg Sauber-Ferrari 1m28.560s +1.254s 20 9. Daniel Ricciardo Toro Rosso-Ferrari 1m28.739s +1.433s 20 10. Romain Grosjean Lotus-Renault 1m28.891s +1.585s 12 11. Fernando Alonso Ferrari 1m28.928s +1.622s 10 12. Esteban Gutierrez Sauber-Ferrari 1m29.049s +1.743s 17 13. Paul di Resta Force India-Mercedes 1m29.174s +1.868s 11 14. Pastor Maldonado Williams-Renault 1m29.717s +2.411s 13 15. Adrian Sutil Force India-Mercedes 1m29.783s +2.477s 7 16. Valtteri Bottas Williams-Renault 1m30.425s +3.119s 15 17. Sergio Perez McLaren-Mercedes 1m30.748s +3.442s 8 18. Jules Bianchi Marussia-Cosworth 1m31.061s +3.755s 18 19. Giedo van der Garde Caterham-Renault 1m31.118s +3.812s 16 20. Charles Pic Caterham-Renault 1m31.165s +3.859s 15 21. Max Chilton Marussia-Cosworth 1m31.211s +3.905s 19 22. Jenson Button McLaren-Mercedes 1m31.770s +4.464s 6