Jenson Button set the pace in the first free practice session for the German Grand Prix at Hockenheim as McLaren used its updated MP4-27 on track for the first time.
The Briton's 1m16.595s lap was 0.498sec faster than his teammate Lewis Hamilton, with championship leader Fernando Alonso third on the time sheets for Ferrari.
Intermittent rain showers rendered times fairly irrelevant in terms of determining form, with teams frequently having to cut short evaluation runs for the updates they have brought to Germany. Button's time was set when the track was completely dry in the first 20 minutes of the 90.
Of the established runners, only he and Lotus driver Romain Grosjean got their programs running before precipitation played its part. When Sergio Perez, Mark Webber and Heikki Kovalainen all then ran wide, however, it was a clear signal that the asphalt was no longer dry and this set a pattern for the rest of the session.
With short, sharp showers dampening the track and then warm ambient temperatures quickly drying it again, the surface became dry enough for teams to continue, if somewhat stutteringly, with their programs on the medium and soft compounds. During this point, Nico Hulkenberg and Alonso improved to go second and third behind Button. Unsurprisingly, almost every driver had a moment at some point as the grips levels changed constantly.
The heaviest of these showers came 20 minutes before the end, prompting Sauber's Perez and Kamui Kobayashi – who had a significant moment running across the gravel early on – to try intermediates. That plan was swiftly spoiled after an exploratory lap each. The last 10 minutes provided some of the driest running and also a flurry of activity on the timing board as Hamilton went second quickest to make it a McLaren 1-2. Alonso improved again to go third with Michael Schumacher's Mercedes fourth.
Perez also squeezed ahead of Hulkenberg before Valtteri Bottas crashed Bruno Senna's Williams at the Sachs Kurve with three minutes to go. That scuppered any hope of anyone going quicker through the final sector - including Hamilton, who was fastest of all through S2 on his final lap. Nico Rosberg was seventh ahead of Felipe Massa, Pastor Maldonado and Grosjean.
The Red Bulls had a low-key session, with world champion Sebastian Vettel 12th and Webber 20th. Kimi Raikkonen was 15th in the Lotus, running with the new double DRS system, having only completed 14 laps in total.
Pos Driver Team Time Laps
1. Jenson Button McLaren-Mercedes 1m16.595 27
2. Lewis Hamilton McLaren-Mercedes 1m17.093s + 0.498 22
3. Fernando Alonso Ferrari 1m17.370s + 0.775 21
4. Michael Schumacher Mercedes 1m17.382s + 0.787 20
5. Sergio Perez Sauber-Ferrari 1m17.413s + 0.818 28
6. Nico Hulkenberg Force India-Mercedes 1m17.599s + 1.004 17
7. Nico Rosberg Mercedes 1m17.915s + 1.320 27
8. Felipe Massa Ferrari 1m17.995s + 1.400 22
9. Pastor Maldonado Williams-Renault 1m18.020s + 1.425 20
10. Romain Grosjean Lotus-Renault 1m18.130s + 1.535 21
11. Kamui Kobayashi Sauber-Ferrari 1m18.226s + 1.631 22
12. Sebastian Vettel Red Bull-Renault 1m18.339s + 1.744 21
13. Valtteri Bottas Williams-Renault 1m18.422s + 1.827 28
14. Daniel Ricciardo Toro Rosso-Ferrari 1m18.709s + 2.114 30
15. Kimi Raikkonen Lotus-Renault 1m18.831s + 2.236 14
16. Jules Bianchi Force India-Mercedes 1m18.972s + 2.377 21
17. Jean-Eric Vergne Toro Rosso-Ferrari 1m19.039s + 2.444 34
18. Vitaly Petrov Caterham-Renault 1m19.674s + 3.079 24
19. Heikki Kovalainen Caterham-Renault 1m19.963s + 3.368 24
20. Mark Webber Red Bull-Renault 1m20.122s + 3.527 27
21. Charles Pic Marussia-Cosworth 1m20.169s + 3.574 20
22. Timo Glock Marussia-Cosworth 1m20.539s + 3.944 18
23. Pedro de la Rosa HRT-Cosworth 1m21.138s + 4.543 24
24. Dani Clos HRT-Cosworth 1m21.740s + 5.145 27
All Timing Unofficial