MW Arden's Mattias Laine set the pace on GP3's first day of mid-season testing at Valencia.
The Finn was fastest almost immediately, before gradually working his way down to a 1m26.610s in the morning session.
That proved unmatched for the remainder of the day, although three other drivers were able to get within one tenth of a second of his benchmark.
Daniel Abt (Lotus GP) came closest to deposing Laine, lapping within three thousandths of a second, while Tio Ellinas (Manor) and Laine's Arden team-mate David Fumanelli also threatened, finishing third and fourth respectively.
Monaco race winner Marlon Stockinger (Status), Antonio Felix da Costa (Carlin) and Barcelona winner Conor Daly (Lotus GP) rounded out the top seven, the trio - like those above them - all setting their fastest times in the morning.
Trident's Nico Muller, returning to the series for testing duties only, was one of the rare few to improve in the second session. Tenth fastest in the morning, he posted a 1m26.865s in the afternoon, enough to top the session and end the day eighth fastest overall, ahead of Patric Niederhauser (Jenzer) and the third Arden of Mitch Evans.
Manor's Fabiano Machado was the cause of two red flags - the first in the morning when he made a visit to the gravel trap, the second in the afternoon when he stopped out on track. Laine and current championship leader Aaro Vainio (Lotus GP) also stopped on circuit late on.
On her series debut Samin Gomez (Jenzer) finished 22nd and 21st field in the respective sessions.
Morning session: Pos Driver Team Time Gap 1. Matias Laine MW Arden 1m26.610s 2. Daniel Abt Lotus 1m26.613s + 0.003s 3. Tio Ellinas Manor 1m26.629s + 0.019s 4. David Fumanelli MW Arden 1m26.686s + 0.076s 5. Marlon Stockinger Status 1m26.725s + 0.115s 6. Antonio Felix da Costa Carlin 1m26.817s + 0.207s 7. Conor Daly Lotus 1m26.836s + 0.226s 8. Patric Niederhauser Jenzer 1m26.932s + 0.322s 9. Mitch Evans MW Arden 1m27.134s + 0.524s 10. Nico Muller Trident 1m27.317s + 0.707s 11. Robert Visoiu Jenzer 1m27.323s + 0.713s 12. William Buller Carlin 1m27.332s + 0.722s 13. Aaro Vainio Lotus 1m27.516s + 0.906s 14. Kevin Ceccon Ocean 1m27.524s + 0.914s 15. Tamas Pal Kiss Atech CRS 1m27.579s + 0.969s 16. Antonio Spavone Trident 1m27.651s + 1.041s 17. Dmitry Suranovich Manor 1m28.043s + 1.433s 18. Fabiano Machado Manor 1m28.142s + 1.532s 19. Vicky Piria Trident 1m28.217s + 1.607s 20. Ethan Ringel Atech CRS 1m29.047s + 2.437s 21. Alice Powell Status 1m29.067s + 2.457s 22. Samin Gomez Jenzer 1m29.179s + 2.569s 23. John Wartique Atech CRS 1m29.493s + 2.883s 24. Robert Cregan Ocean 1m29.672s + 3.062s 25. Carmen Jorda Ocean 1m30.512s + 3.902s Afternoon session: Pos Driver Team Time Gap 1. Nico Muller Trident 1m26.865s 2. Antonio Felix da Costa Carlin 1m27.046s + 0.181s 3. Tio Ellinas Manor 1m27.663s + 0.798s 4. David Fumanelli MW Arden 1m27.721s + 0.856s 5. Kevin Ceccon Ocean 1m27.723s + 0.858s 6. Conor Daly Lotus 1m27.785s + 0.920s 7. Robert Visoiu Jenzer 1m27.842s + 0.977s 8. Mitch Evans MW Arden 1m27.870s + 1.005s 9. Matias Laine MW Arden 1m27.912s + 1.047s 10. Daniel Abt Lotus 1m27.982s + 1.117s 11. William Buller Carlin 1m27.990s + 1.125s 12. Aaro Vainio Lotus 1m28.059s + 1.194s 13. Patric Niederhauser Jenzer 1m28.144s + 1.279s 14. Dmitry Suranovich Manor 1m28.417s + 1.552s 15. Ethan Ringel Atech CRS 1m28.515s + 1.650s 16. Antonio Spavone Trident 1m28.693s + 1.828s 17. Tamas Pal Kiss Atech CRS 1m28.901s + 2.036s 18. Vicky Piria Trident 1m29.003s + 2.138s 19. Alice Powell Status 1m29.022s + 2.157s 20. John Wartique Atech CRS 1m29.045s + 2.180s 21. Samin Gomez Jenzer 1m29.132s + 2.267s 22. Fabiano Machado Manor 1m29.481s + 2.616s 23. Marlon Stockinger Status 1m29.694s + 2.829s 24. Robert Cregan Ocean 1m29.920s + 3.055s 25. Carmen Jorda Ocean 1m31.040s + 4.175s