Toro Rosso's Sebastian Vettel was a surprise fastest in first practice at the European Grand Prix.
McLaren's Lewis Hamilton was the early pace-setter at the new Valencia track but the Englishman spun on what was looking set to be his fastest lap.
Vettel had just beaten Hamilton's mark, and the German went faster again to set a one minute 40.496 seconds best.
Ferrari's Felipe Massa was 0.158secs adrift, with Hamilton third followed by Vettel's team-mate Sebastien Bourdais.
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But there were no major crashes despite the concrete walls lining the track.
The Toro Rosso cars put on new tyres at the end of the session while the front-runners did not, which would have flattered their competitiveness.
They are not expected to be major contenders for victory on Sunday.
Ferrari's Kimi Raikkonen was fastest after the drivers had been out for their first exploratory timed laps, but the world champion ended the session seventh.
McLaren's Heikki Kovalainen and BMW Sauber's Robert Kubica, who were both fastest at various points during the 90 minutes of action split Raikkonen from Bourdais.
Hamilton looked the man to beat as soon as the cars went out for their second runs, with a series of impressive laps keeping him clear of the field.
And although Vettel then displaced the world championship leader at the top of the time sheets with a few minutes to go, Hamilton looked set to displace him - he set the fastest first sector time before losing control while braking for a right right-hander.
The Red Bulls of David Coulthard and Mark Webber brought up the rear, despite being fundamentally the same car as the Toro Rosso, albeit with a different engine.
Webber, BBC Sport's columnist, admitted the team were struggling, but he said he was enjoying the track and that he expected it to produce an exciting race with a number of interventions by the safety car.
"It's a good street circuit," Webber said. "I'm enjoying driving round it. I'm not enjoying seeing the lap times!
"We had a tough first session. We've got a lot of work to do because we are definitely not quick enough at all, David and I.
"There are not many fast corners, but the straights are quite quick with a few kinks on them. It's quicker than the normal street circuit. They've done a good job with it.
"The first part of the track is a bit like Montreal, with a lot of chicanes, but after that it's sort of a street circuit of its own.
"I think we'll have a safety car or two in the race, which can blow the results around a bit. But, hey, if we're on the receiving end of a bit of luck this time, why not?"
Times from first practice at European Grand Prix at Valencia:
1 Sebastian Vettel (Ger) Toro Rosso-Ferrari one minute 40.496 seconds
2 Felipe Massa (Brz) Ferrari 1:40.654
3 Lewis Hamilton (GB) McLaren-Mercedes 1:40.822
4 Sebastien Bourdais (Fra) 1:41.099
5 Heikki Kovalainen (Fin) McLaren-Mercedes 1:41.163
6 Robert Kubica (Pol) BMW Sauber 1:41.281
7 Kimi Raikkonen (Fin) Ferrari 1:41.317
8 Kazuki Nakajima (Jpn) Williams-Toyota 1:41.329
9 Fernando Alonso (Spa) Renault 1:41.385
10 Nico Rosberg (Ger) Williams-Toyota 1:41.706
11 Rubens Barrichello (Brz) Honda 1:41.830
12 Jarno Trulli (Ita) Toyota 1:41.930
13 Adrian Sutil (Ger) Force India-Ferrari 1:41.951
14 Timo Glock (Ger) Toyota 1:42.036
15 Nelson Piquet Jr (Brz) Renault 1:42.107
16 Nick Heidfeld (Ger) BMW Sauber 1:42.453
17 Jenson Button (GB) Honda 1:42.460
18 Giancarlo Fisichella (Ita) Force India-Ferrari 1:43.075
19 David Coulthard (GB) Red Bull-Renault 1:43.312
20 Mark Webber (Aus) Red Bull-Renault 1:43.524
(BBC)
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