Red Bull and Ferrari led the way in Friday's second free practice session at Monza, with Sebastian Vettel and Fernando Alonso setting the pace.
McLaren had looked untouchable for the majority of the session with Lewis Hamilton and Jenson Button three quarters of a second faster than anyone else. But both Ferrari and Red Bull sent their drivers out for low-fuel, soft-tire runs with half an hour to go, and both teams were able to better McLaren's pace.
Felipe Massa initially went quickest, though his time was soon beaten by Vettel. Then Alonso leaped to the top only for Vettel to respond again, this time with a 1m22.8sec.
Massa had to call an early halt to his low fuel run after a scary moment at the final corner. The Brazilian looked set to beat Vettel's time, having set personal bests in the first and second sectors, but dropped a wheel off the track exiting the Parabolica, slid into the gravel and only just kept his Ferrari out of the wall. But he remained third quickest, as the leading teams reverted to higher fuel runs at the end.
Button kept McLaren's F-duct on his car this afternoon and ended up fourth, while Hamilton drove without it and was fifth. Toro Rosso also removed the device from its cars.
Mark Webber finished FP2 sixth quickest but, as in the day's earlier session, struggled to match the pace of the other front runners. He was denied an opportunity to improve when the Red Bull team ordered him to stop his car on track at the first Lesmo with 18 minutes to go, due to a loss of water pressure.
The Williams of Rubens Barrichello and Nico Hulkenberg sandwiched Robert Kubica's Renault in seventh and ninth, with Nico Rosberg's Mercedes rounding out the top 10.
Adrian Sutil was 11th having reclaimed his Force India from Paul di Resta, ahead of teammate Vitantonio Liuzzi and the second Renault and Mercedes of Vitaly Petrov and Michael Schumacher.
Jaime Alguersuari's practice came to an early end with just under half an hour remaining when his car stopped out on track as he exited the second chicane.
Lotus was the faster of the new teams this afternoon, both Jarno Trulli and Heikki Kovalainen ahead of the two Virgins. Bruno Senna is still yet to turn any meaningful laps of Monza today after another problem-filled practice. His Hispania stopped with a loss of fuel pressure just yards from his pit garage at the beginning of the session. After another failed attempt mid-way through practice, he finally made it onto track with 10 minutes remaining only to park up at Turn 2 on his out-lap.
The second HRT of Sakon Yamamoto completed just five laps.
Pos Driver Team Time Laps
1. Vettel, Red Bull-Renault, 1:22.839 27
2. Alonso, Ferrari, 1:22.915 + 0.076 32
3. Massa, Ferrari, 1:23.061 + 0.222 20
4. Hamilton, McLaren-Mercedes, 1:23.154 + 0.315 22
5. Button, McLaren-Mercedes, 1:23.210 + 0.371 38
6. Webber, Red Bull-Renault, 1:23.415 + 0.576 23
7. Barrichello, Williams-Cosworth, 1:23.708 + 0.869 31
8. Kubica, Renault, 1:23.709 + 0.870 32
9. Hulkenberg, Williams-Cosworth, 1:23.852 + 1.013 30
10. Rosberg, Mercedes, 1:23.857 + 1.018 29
11. Sutil, Force India-Mercedes, 1:24.181 + 1.342 35
12. Liuzzi, Force India-Mercedes, 1:24.380 + 1.541 36
13. Petrov, Renault, 1:24.407 + 1.568 21
14. Schumacher, Mercedes, 1:24.448 + 1.609 29
15. Buemi, Toro Rosso-Ferrari, 1:24.517 + 1.678 35
16. De la Rosa, Sauber-Ferrar, 1:24.547 + 1.708 32
17. Kobayashi, Sauber-Ferrari, 1:24.785 + 1.946 31
18. Alguersuari, Toro Rosso-Ferrari, 1:25.106 + 2.267 24
19. Trulli, Lotus-Cosworth, 1:26.204 + 3.365 38
20. Kovalainen, Lotus-Cosworth, 1:26.306 + 3.467 41
21. di Grassi, Virgin-Cosworth, 1:26.631 + 3.792 31
22. Glock, Virgin-Cosworth, 1:26.676 + 3.837 25
23. Yamamoto, HRT-Cosworth, 1:29.498 + 6.659 5
24. Senna, HRT-Cosworth, 3