Sebastian Vettel was quickest again in the second Friday practice session for the Australian Grand Prix, this time leading team-mate Mark Webber in a Red Bull one-two.
Vettel, who had also led the morning session, was quickest for the majority of the afternoon, leading by a second early on.
Webber nosed ahead briefly during the super-soft runs, before Vettel took the top spot with a 1m25.908s lap, 0.264 seconds ahead of the Australian.
The teams all switched to heavy fuel runs soon after. Tyre degradation appeared severe, with lap times on short runs dropping off dramatically after the first flying laps, and the pace on longer stints slowing considerably.
Tyre wear looked like it was a factor in a late-session spin for Webber, who lost grip on the exit of Turn 13 and slid sideways and backwards down the track.
Mercedes showed encouraging pace but also had issues.
Nico Rosberg took third fastest, before stopping on track in the closing moments with a suspected gearbox failure.
His team-mate Lewis Hamilton was seventh. A potentially better lap was interrupted with a trip over the Turn 9 gravel and grass, and he later ploughed into the gravel just minutes before Rosberg had his issue.
Also in trouble were Jean-Eric Vergne, who spun his Toro Rosso across the asphalt run-off, and Giedo van der Garde, who spun off at Turn 6 and got stuck in the gravel with an hour to go.
Lotus got both cars in the top five, with Kimi Raikkonen ahead of Romain Grosjean in fourth.
Fernando Alonso and Felipe Massa's Ferraris were sixth and eighth, followed by Adrian Sutil and Nico Hulkenberg.
Pos Driver Team Time Gap Laps
1. Sebastian Vettel Red Bull-Renault 1m25.908 33
2. Mark Webber Red Bull-Renault 1m26.172s + 0.264 31
3. Nico Rosberg Mercedes 1m26.322s + 0.414 26
4. Kimi Raikkonen Lotus-Renault 1m26.361s + 0.453 37
5. Romain Grosjean Lotus Renault 1m26.680s + 0.772 30
6. Fernando Alonso Ferrari 1m26.748s + 0.840 35
7. Lewis Hamilton Mercedes 1m26.772s + 0.864 28
8. Felipe Massa Ferrari 1m26.855s + 0.947 32
9. Adrian Sutil Force India-Mercedes 1m27.435s + 1.527 34
10. Nico Hulkenberg Sauber-Ferrari 1m28.187s + 2.279 34
11. Jenson Button McLaren-Mercedes 1m28.294s + 2.386 30
12. Paul di Resta Force India-Mercedes 1m28.311s + 2.403 37
13. Sergio Perez McLaren-Mercedes 1m28.566s + 2.658 32
14. Daniel Ricciardo Toro Rosso-Ferrari 1m28.627s + 2.719 31
15. Esteban Gutierrez Sauber-Ferrari 1m28.772s + 2.864 33
16. Pastor Maldonado Williams-Renault 1m28.852s + 2.944 36
17. Jean-Eric Vergne Toro Rosso-Ferrari 1m28.968s + 3.060 35
18. Valtteri Bottas Williams-Renault 1m29.386s + 3.478 38
19. Jules Bianchi Marussia-Cosworth 1m29.696s + 3.788 30
20. Charles Pic Caterham-Renault 1m30.165s + 4.257 37
21. Max Chilton Marussia-Cosworth 1m30.600s + 4.692 34
22. Giedo van der Garde Caterham-Renault 1m32.450s + 6.542 11