Ferrari's Charles Leclerc completed a practice hat-trick at the Spanish Grand Prix.
The championship leader edged out Red Bull's Max Verstappen by just seven hundredths, with the Mercedes duo of George Russell and Lewis Hamilton third and fourth, respectively.
Carlos Sainz finished fifth, one spot ahead of Sergio Perez at a sweltering Circuit de Catalunya, 26km north of Barcelona.
Leclerc, who holds a 19-point title advantage over Verstappen ahead of Sunday's sixth round, has dominated all three practice sessions.
But the Ferrari driver will have Verstappen – winner of the past two races in Imola and Miami – hot on his heels for qualifying.
Both Mercedes cars could also be in the hunt, with Russell just 0.148secs back from Leclerc and Hamilton a quarter-of-a-second adrift.
The Silver Arrows have brought several upgrades to Spain – including a revised floor and new front wing – and the early signs are encouraging for the team, which has won the last eight constructors' championships.
Russell is 23 points ahead of teammate Hamilton after beating his seven-time world championship-winning teammate at four of the five grands prix.
And Hamilton, 37, trailed the younger Briton, 24, in the final one-hour running before qualifying.
"The sectors you gave me, is that to the fastest (driver) or to (George)?" asked Hamilton over the team radio.
"That's to George, so that is best sectors to George," answered his race engineer Peter Bonnington.
A tetchy Hamilton replied: "I only ever want to know the fastest."
Mick Schumacher's right-rear brakes caught on fire in the early moments, with the German's Haas team now facing a race against time to ensure his machine is ready to return to the track on Saturday afternoon.
Spanish GP FP3 results:
POS DRIVER TEAM TIME
1 Charles Leclerc - Scuderia Ferrari 1m19.772s
2 Max Verstappen - Oracle Red Bull Racing 1m19.844s
3 George Russell - Mercedes AMG Petronas Formula One Team 1m19.920s
4 Lewis Hamilton - Mercedes AMG Petronas Formula One Team 1m20.002s
5 Carlos Sainz - Scuderia Ferrari 1m20.129s
6 Sergio Perez - Oracle Red Bull Racing 1m20.260s
7 Lando Norris - McLaren F1 Team 1m20.403s
8 Kevin Magnussen - Haas F1 Team 1m20.646s
9 Valtteri Bottas - Alfa Romeo F1 Team Orlen 1m20.781s
10 Esteban Ocon - BWT Alpine F1 Team 1m20.882s
11 Daniel Ricciardo - McLaren F1 Team 1m20.910s
12 Sebastian Vettel - Aston Martin Aramco Cognizant Formula One Team 1m20.944s
13 Fernando Alonso - BWT Alpine F1 Team 1m20.981s
14 Guanyu Zhou - Alfa Romeo F1 Team Orlen 1m21.201s
15 Yuki Tsunoda - Scuderia AlphaTauri 1m21.449s
16 Lance Stroll - Aston Martin Aramco Cognizant Formula One Team 1m21.520s
17 Alexander Albon - Williams Racing 1m21.572s
18 Nicholas Latifi - Williams Racing 1m22.419s
19 Mick Schumacher - Haas F1 Team 1m25.467s
20 Pierre Gasly - Scuderia AlphaTauri No Time Set