Lewis Hamilton put Mercedes in their customary position on top of the timing screens in the first practice session at the Circuit de Catalunya.
The winner of the last three races reeled off a pair of flying laps in the final minutes of the session to end up quickest on a 1’27.023.
But team mate Nico Rosberg only did nine laps after the team discovered a problem with his energy recovery system.
Jenson Button was second-fastest having headed much of the session in his McLaren.
Daniel Ricciardo and Fernando Alonso made it four different cars in the top four. But there were problems for the other Red Bull.
The session was only a few minutes old when Sebastian Vettel’s RB10 came to a stop at turn six. He kept a close eye on the rear of his car, fire extinguisher at the ready, before it was returned to the pits. But he took no further part in practice.
Giedo van der Garde had a scare when he suffered a suspected brake failure at turn one. He hurtled across the gravel trap and came close to hitting the barrier before recovering to the pits.
2014 Spanish Grand Prix
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2014 F1 practice sessions
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Image © Daimler/Hoch Zwei