Max Verstappen will go to the season-opening Bahrain Grand Prix with the fastest time from testing after putting Red Bull top of the order on the final day.
Questions linger over world champions Mercedes, who looked out of sorts across the three days.
It was the final day of track action at the Bahrain International Circuit ahead of the opening race at the same venue on March 28.
Max Verstappen underlined the growing belief that Red Bull will be the team to beat at the first race. Verstappen's fastest time of 1:28.960, set on the C4 compound tyre late on, led the way when the session drew to a close.
Mercedes focused on heavy-fuel runs for most of the day. Lewis Hamilton moved onto the softer compounds late on and spun before one attempt on the C5 compound. His quickest time was over a second slower than Verstappen's, further clouding the picture at the front of the order. Differing fuel loads and engine maps could explain the gap, but there is no reason to believe Red Bull was running its car on significantly lower fuel.
Yuki Tsunoda capped an impressive test for AlphaTauri by finishing second, marginally slower than Verstappen in the other Honda-powered car. The AlphaTauri features a similar aerodynamic concept and shares some parts with Red Bull, suggesting F1's new regulations may have shifted the advantage towards the two Red Bull-owned teams.
Aston Martin also seemed to be focused on heavy-fuel running and did not test the softer compounds on Sunday. Sebastian Vettel was forced to jump out of the car with 90 minutes remaining when the team discovered a turbo issue on the Mercedes power unit. Combined with the gearbox issue that limited Vettel's running on Saturday, the four-time world champion heads to the first race without the mileage he was hoping for.
In the final seconds of the session, new Ferrari signing Carlos Sainz almost collided with Alfa Romeo's Kimi Raikkonen in a bizarre moment at Turn 10. Sainz overtook Raikkonen on the inside of the corner but had to change his line to avoid a collision. The two cars then ran very close to each other and raced aggressively through the remainder of the lap as they headed back to the pits.
There were no red flag stoppages during the session, underlining the impressive reliability of the ten teams after three days of testing.
Each team has just one car at the test, but several alternated drivers either side of the lunch break.
1. Max Verstappen - Red Bull - 1:28.960 (C4) - 64 laps
2. Yuki Tsunoda - Alpha Tauri - +0.093s (C5) - 90 laps
3. Carlos Sainz - Ferrari - +0.651s (C4) - 78 laps
4. Kimi Raikkonen - Alfa Romeo - +0.806s (C5) - 164 laps
5. Lewis Hamilton - Mercedes - +1.065s (C5) - 54 laps
6. George Russell - Williams - +1.157s (C5) - 157 laps
7. Daniel Ricciardo - McLaren - +1.184s (C4) - 74 laps
8. Sergio Perez - Red Bull - +1.227s (C4) - 49 laps
9. Fernando Alonso - Alpine - +1.358s (C4) - 76 laps
10. Charles Leclerc - Ferrari - +1:526s (C3) - 80 laps
11. Lando Norris - McLaren - +1.701s (C3) - 56 laps
12. Pierre Gasly - AlphaTauri - +1.868s (C4) - 76 laps
13. Esteban Ocon - Alpine - +2.350s (C3) - 61 laps
14. Nikita Mazepin - Haas - +2.571s (C4) - 67 laps
15. Mick Schumacher - Haas - +3.093s (C3) - 78 laps
16. Valtteri Bottas - Mercedes - +3.446s (C2) - 86 laps
17. Sebastian Vettel - Aston Martin - +6.081s (C3) - 56 laps
18. Lance Stroll - Aston Martin - +7.140s (C3) - 80 laps
Total lap count over three days
1= Alfa Romeo 422
1= AlphaTauri 422
3. Ferrari 404
4. Alpine 396
5. Haas 394
6. Williams 373
7. Red Bull 369
8. McLaren 327
9. Aston Martin 314
10. Mercedes 304