Red Bull continued its strong form from Silverstone in the opening practice session for the German Grand Prix, as Mark Webber set the fastest time at a chilly and overcast Nurburgring.
Championship leader Jenson Button took second for Brawn GP, ahead of Ferrari's Felipe Massa.
But it was a tough session for Webber's team-mate Sebastian Vettel, whose car ground to a halt at the first corner after 10 laps. Although it was fixed in time for him to rejoin in the closing minutes, he was unable to improve on his eighth-fastest time in the single flying lap he managed.
Early drizzle meant it was approaching the halfway point of the session before the running started in earnest, with Jarno Trulli (Toyota) and Nico Rosberg (Williams) getting embroiled in an early battle for superiority until Webber hit the front with a 1m34.444s lap after 46 minutes.
The Australian then repeatedly improved his time, edging clear whenever anyone closed in, to end the morning with a benchmark time of 1m33.082s, although he had set even better sector times on several laps near the end.
Button eventually got within 0.381s of Webber with a late improvement, while third placed Massa was 0.663s off the leader's pace.
Trulli ended the morning in fourth, ahead of Giancarlo Fisichella, as Force India again displayed extremely impressive practice pace. The Italian had run as high as second earlier in the session.
While Fisichella shone, his team-mate Adrian Sutil spent most of the morning watching from the sidelines. His Force India appeared to lose drive on its seventh lap of the day, coming to a halt at the first corner a few minutes before his countryman Vettel did likewise. Unlike Vettel, Sutil was unable to get back out again.
Kimi Raikkonen made it two Ferraris in the top six, ahead of Rosberg, Vettel, Kazuki Nakajima (Williams) and Fernando Alonso (Renault).
It was a strange morning for Button's team-mate Rubens Barrichello. The Brazilian was slowest for much of the session, and then made several small errors when he came out for his final run, before eventually hauling himself up to 12th.
Pos Driver Team Time Laps
1. Webber Red Bull-Renault (B) 1:33.082 19
2. Button Brawn-Mercedes (B) 1:33.463 + 0.381 18
3. Massa Ferrari (B) 1:33.745 + 0.663 21
4. Trulli Toyota (B) 1:33.795 + 0.713 23
5. Fisichella Force India-Mercedes (B) 1:33.839 + 0.757 26
6. Raikkonen Ferrari (B) 1:33.840 + 0.758 23
7. Rosberg Williams-Toyota (B) 1:33.902 + 0.820 26
8. Vettel Red Bull-Renault (B) 1:33.909 + 0.827 13
9. Nakajima Williams-Toyota (B) 1:33.952 + 0.870 25
10. Alonso Renault (B) 1:34.148 + 1.066 16
11. Heidfeld BMW-Sauber (B) 1:34.221 + 1.139 25
12. Barrichello Brawn-Mercedes (B) 1:34.227 + 1.145 17
13. Hamilton McLaren-Mercedes (B) 1:34.483 + 1.401 14
14. Kubica BMW-Sauber (B) 1:34.694 + 1.612 23
15. Piquet Renault (B) 1:34.738 + 1.656 24
16. Bourdais Toro Rosso-Ferrari (B) 1:34.827 + 1.745 27
17. Buemi Toro Rosso-Ferrari (B) 1:34.878 + 1.796 28
18. Kovalainen McLaren-Mercedes (B) 1:34.893 + 1.811 26
19. Glock Toyota (B) 1:34.911 + 1.829 23
20. Sutil Force India-Mercedes (B) 1:35.092 + 2.010 6
All Timing Unofficial