Charles Leclerc topped both practices in Barcelona on day one but Mercedes showed massive improvements to finish second and third on the time charts.
With the track temperatures reaching 45 degrees teams opted for softer compounds as the serious business of qualifying simulations began.
The defending champion Max Verstappen threw down the early gauntlet with a 1m 20.006s.
After leading FP1, Leclerc bettered the Dutchman and set the session benchmark of 1m 19.670s, to complete a clean sweep of best times from Friday in his upgraded Ferrari F1-75.
Leclerc is hoping he can do well in Barcelona to hold off the charge of Verstappen who has momentum on his side.
He was followed by the Mercedes duo of George Russell and Lewis Hamilton as their upgraded W13s showed massive improvements.
Russell took P2, 0.117s off Leclerc’s pace, and less than a tenth up on teammate Hamilton.
That left Carlos Sainz P4, with Verstappen ultimately taking P5 with the reigning champion only 0.336s off his championship rival Leclerc.
Fernando Alonso followed his countryman in P6 ahead of the second Red Bull of Sergio Perez who was in his first session of the day after giving up his car to Juri Vips for FP1.
Sebastian Vettel took P8 in another heavily updated Aston Martin AMR22 followed by Esteban Ocon with Mick Schumacher rounding out the top 10.
