Championship leader Lewis Hamilton posted the fastest lap in final practice for the Spanish Grand Prix
The world champion, who holds a 30-point title lead over Red Bull's Max Verstappen, finished 0.151 seconds clear of Mercedes team-mate Valtteri Bottas.
Verstappen was third, half-a-second down on Hamilton, and ahead of McLaren's Carlos Sainz and Racing Point driver Sergio Perez.
Mercedes have topped all three practice sessions at Barcelona's Circuit de Catalunya as the world champions bid to bounce back from their first defeat of the season at Silverstone's 70th Anniversary Grand Prix last weekend.
And they will head into qualifying holding a healthy advantage over the rest of the pack, with Hamilton and Bottas primed to contend pole position for the sixth time in as many rounds this year.
The one-hour session was red-flagged in the final few minutes after Esteban Ocon crashed out in his Renault.
The French driver slammed his car into the wall on the exit of turn three in a bid to avoid the slowing Kevin Magnussen.
Ocon emerged unscathed from the curious accident but he suffered sufficient damage to the front of his Renault.
Asked by his team to explain what happened, Ocon said: "I let Magnussen past because he was on a timed lap and then he decelerated."
The incident is under investigation by the stewards.
Elsewhere, Ferrari's Charles Lelcerc finished sixth, with Sebastian Vettel only 12th, 1.5secs slower than Hamilton, and half-a-second off his team-mate.
