Kevin Ceccon set the pace for MW Arden on the opening day of GP3's post-season test at Jerez.
The 19-year-old Italian, who finished ninth in this year's championship while driving for Ocean, lapped the Spanish track in 1m35.451s to end the day more than half a second clear of the field.
Afternoon rain prevented anyone from mustering a late response, meaning Robert Visoiu's 1m35.903s remained good enough for second.
Tio Ellinas, fastest in the wet, ended the day in third ahead of David Fumanelli, Melville McKee and Alex Fontana.
McKee was the quickest newcomer in the 20-car field, which featured six drivers from the regular season.
British F3 champion Jack Harvey, making his series debut with Carlin, was 14th fastest in the morning and second fastest, less than half a second down on Ellinas, in the afternoon.
Pos Driver Team Time Gap
1. Kevin Ceccon MW Arden 1m35.451s
2. Robert Visoiu Lotus 1m35.903s + 0.452s
3. Tio Ellinas Manor 1m36.009s + 0.558s
4. David Fumanelli MW Arden 1m36.090s + 0.649s
5. Melville McKee MW Arden 1m36.346s + 0.895s
6. Alex Fontana Jenzer 1m36.460s + 1.009s
7. Nick Cassidy Status 1m36.483s + 1.031s
8. Nicolas Costa Manor 1m36.565s + 1.114s
9. Miki Weckstrom Status 1m36.608s + 1.157s
10. Roman de Beer Trident 1m36.715s + 1.264s
11. Giovanni Venturini Lotus 1m36.763s + 1.312s
12. Eric Lichtenstein Carlin 1m36.823s + 1.372s
13. Josh Webster Carlin 1m37.045s + 1.594s
14. Jack Harvey Lotus 1m37.053s + 1.602s
15. Miki Monras Atech CRS 1m37.146s + 1.695s
16. Patryk Szczerbinski Manor 1m37.414s + 1.956s
17. Emanuele Zonzini Trident 1m37.427s + 1.969s
18. Jordan Oon Atech CRS 1m37.695s + 2.244s
19. Samin Gomez Jenzer 1m38.217s + 2.764s
20. Ryan Cullen Status 1m38.706s + 3.265s