Lewis Hamilton clocked the fastest time in second practice for this weekend's Spanish Grand Prix.
Mercedes team-mate Valtteri Bottas beat Hamilton to top spot in the first running at Barcelona's Circuit de Catalunya on Friday morning.
But Hamilton, who holds a 30-point championship lead ahead of the sixth round of the season, ended the final track action of the day 0.287 seconds faster than the Finn.
While Red Bull's Max Verstappen curtailed Mercedes' winning streak with a fine victory at the 70th Anniversary Grand Prix at Silverstone last weekend, the Dutchman finished a distant third.
He was eight tenths behind Hamilton with Renault's Daniel Ricciardo the only other driver to be within one second of the championship leader.
Hamilton and Bottas chewed through their tyres at last weekend's race to allow Verstappen to wrestle the initiative.
And following Mercedes' impressive one-lap speed here, concerns over their rubber in the hot temperatures, which are set to continue throughout the weekend, look likely to provide the biggest threat to a return to the winner's circle for Hamilton on Sunday.
Romain Grosjean finished an impressive fifth for Haas ahead of the Ferrari of Charles Leclerc in sixth.
Four-time world champion Sebastian Vettel is under pressure to deliver for Ferrari after he finished a distant 12th at Silverstone last Sunday to leave him 13th in the standings.
The German was just behind Leclerc in the opening session, but was 12th, three tenths off his team-mate later in the day.
Red Bull's Alexander Albon ended the action in 13th, eight tenths behind Verstappen in the sister Red Bull.
British driver Lando Norris was only 14th, seven spots behind McLaren team-mate and home favourite Carlos Sainz.
George Russell returned to his Williams cockpit after handing the keys over to the British team's development driver Roy Nissany on Friday morning.
But the young Briton propped up the order as he struggled with the handling of his car. "It is like driving on ice" the disgruntled Russell said over the team radio.
