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BARCELONA, Spain -- Robert Kubica does not have a full-time race seat in Formula One in 2020, but the Polish driver topped the fourth day of its preseason tests for Alfa Romeo.

Kubica is Alfa Romeo's reserve driver this year and has been given two stints in the car this preseason. He kicked off the team's winter tests on Feb. 19 and completed the morning session seven days on.

His headline time of 1:16.952 was over a second slower than the benchmark set by Mercedes' Valtteri Bottas last week on Friday, suggesting that the grid's teams were still not pushing the limits of outright performance. Red Bull's Max Verstappen was the next car on the order, finishing 0.405s behind, to further highlight that fact.

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World champion Mercedes continued its habit of churning out laps, with Bottas and Lewis Hamilton combining for 179 laps. However, it was clear mileage and race simulations were the order of the day rather than exploring one-lap pace, meaning it is still difficult to judge the current pecking order across the field.

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The day had only a handful of noteworthy incidents.

Ferrari's Sebastian Vettel managed to avoid a setback when he lost control of the car at Turn 7/8 on the approach up the hill towards Turn 9. The four-time world champion managed to control the spin and keep his car away from the walls that closely line the edge of that part of the circuit. The incident could have severely hampered Ferrari's day, but Vettel finished the morning session with 84 laps to his name -- teammate Charles Leclerc completed another 80 after lunch.

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Red Bull's two teams both had some delays. The Red Bull car was in the garage for a while with a suspension problem, and Alpha Tauri's morning was hampered by an issue with a water pipe. Both cars emerged from the garage around the same time. Alex Albon and Pierre Gasly handed over to their respective teammates, Max Verstappen and Daniil Kvyat, after lunch, and the afternoon pairing had a much more productive time. However, at almost the same moment at the end of the session, both cars stopped: Verstappen had a spin at Turn 10, and Kvyat's car ground to a halt up the Turn 9 hill.

Williams also had a stoppage, which it put down to an oil system problem. It is Williams' third Mercedes-related issue of the preseason so far.

However, overall it remained a productive day for every team. Romain Grosjean was the only centurion, completing 107 laps in the Haas, but he was also the only driver to do the entire session. Every other team swapped its drivers midway through the day.

Final times:

1. Robert Kubica - Alfa Romeo - 1:16.942 - 53 laps

2. Max Verstappen - Red Bull - 1:17.347 - 84 laps

3. Sergio Perez - Racing Point - 1:17.428 - 84 laps

4. Daniil Kvyat - Alpha Tauri - 1:17.456 - 61 laps

5. Pierre Gasly - Alpha Tauri - 1:17.540 - 25 laps

6. Alex Albon - Red Bull - 1:17.550 - 29 laps

7. Lewis Hamilton - Mercedes - 1:17.562 - 89 laps

8. Lance Stroll - Racing Point - 1:17.787 - 43 laps

9. Valtteri Bottas - Mercedes - 1:18.100 - 90 laps

10. Sebastian Vettel - Ferrari - 1:18.113 - 84 laps

11. Daniel Ricciardo - Renault - 1:18.214 - 53 laps

12. Carlos Sainz - McLaren - 1:18.221 - 46 laps

13. Charles Leclerc - Ferrari - 1:18.244 - 80 laps

14. Nicholas Latifi - Williams - 1:18.300 - 48 laps

15. George Russell - Williams - 1:18.535 - 59 laps

16. Romain Grosjean - Haas - 1:18.670 - 56 laps

17. Lando Norris - McLaren - 1:18.826 - 57 laps

18. Kimi Raikkonen - Alfa Romeo - 1:19.515 - 51 laps

19. Esteban Ocon - Renault - 1:21.542 - 74 laps