Lewis Hamilton raised the bar for this week's Spanish Grand Prix by setting the fastest time in second practice on Friday.
Hamilton was beaten to top spot by his Mercedes team-mate Valtteri Bottas in the opening running, but the reigning champion ended the day fastest at Barcelona's sun-bathed Circuit de Catalunya.
The British driver's best effort of one minute and 18.259 seconds enabled him to edge out Daniel Ricciardo by less than two tenths with his Red Bull team-mate Max Verstappen third.
Ricciardo crashed out of opening practice earlier on Friday after he lost control of his Red Bull at Turn 4 and slid helplessly across the sand trap and into the barriers.
But following repairs to his car, the Australian, backed up by Verstappen, ran Hamilton close to suggest Red Bull have the credentials to take the fight to Mercedes and Ferrari.
Ferrari rarely show their true pace on Friday and Sebastian Vettel, who trails Hamilton by four points, finished in fourth, a third of a second down on Hamilton's best time.
Vettel's team-mate Kimi Raikkonen posted the sixth fastest lap, but was told to park his Ferrari after puffs of white smoke came from his engine. Bottas was fifth in the order.
Mercedes, Ferrari and Red Bull have all brought revised cars to this weekend's race with the opening western European round of the season traditionally kick-starting the development war.
And Bottas's early pace - the Finn posted a record-breaking lap of this 2.9-mile track - followed by Hamilton's time in the second session, would indicate Mercedes have taken the greater stride forward with Vettel's Ferrari team having previously boasted the most complete package of the season.
McLaren had also been hopeful that their revised car would curb a downward spiral, but after Fernando Alonso finished a dizzying sixth by trading times with the Red Bull cars in the day's opening running, he was only 12th in the afternoon session.
Saturday marks the fifth anniversary of the Spaniard's last victory in F1, and it is highly likely that he may never win again.
Stoffel Vandoorne was ninth, but there is still significant work to do for the British team, who have failed to get either of their cars into the final phase of qualifying this season.
Robert Kubica is back competing at his first grand prix weekend in more than seven years after suffering career-changing injuries to his right arm in a rally crash.
The Pole, now acting as reserve driver for Williams, was last but one in the opening sessions, 1.3secs ahead of team-mate Lance Stroll.