Australian Mark Webber set the pace in the opening practice session for Sunday's European Grand Prix, the Red Bull driver outpacing his nearest rival by nearly a second on the hybrid street circuit in Valencia.
Webber, keen to re-establish himself as a title contender, stamped his authority on proceedings with a best time of one minute and 40.597 seconds to leave himself clear of Russian Vitaly Petrov, the ever-improving Renault driver.
Local hero Fernando Alonso was third for Ferrari ahead of Briton Lewis Hamilton of McLaren. German Nick Heidfeld completed the top five in the second Renault.
Defending world champion and runaway leader Sebastian Vettel of Germany made a low-key start to his weekend, down in 16th place, more than 2.5 seconds slower than teammate Webber in a session completed without major incident.
Force India's reserve driver German Nico Hulkenberg set the pace early on as few drivers completed a time lap on the track.
But his enterprising start soon ended in pain when he hit the wall on Turn 12 where he lost control of the rear end of his car under braking. He had to limp in for repairs and sit out the rest of the morning, having completed only six laps.
Venezuelan Pastor Maldonado of Williams and Spaniard Jaime Alguersuari of Toro Rosso then posted fastest times before seven-times world champion Michael Schumacher took over top spot.
He was succeeded by Brazilian Felipe Massa in his Ferrari and then Alonso before Webber took control for the final half an hour.