Marvin Kirchhofer topped the timesheets for ART Grand Prix on day one of GP3 Series testing at Valencia.
With a time of 1m21.098s, Kirchhofer, who is the highest placed championship returnee after finishing third last year, finished the afternoon session two tenths ahead of closest rival Luca Ghiotto.
Rookie Alex Palou topped the morning session for Campos Racing with a time of 1m21.269s. The former Euroformula Open driver also impressed in the afternoon, finishing the session in fourth behind Esteban Ocon.
Kevin Korjus returned to Koiranen GP for the test standing in for Adderly Fong who had Lotus F1 Team commitments. The Estonian finished the afternoon session in fifth.
Returning from his devastating accident at the Nurburgring, Jann Mardenborough only featured in the top ten during the morning session in seventh. Finishing as the highest placed Carlin of both sessions.
The top 17 drivers were separated by less than a second in the afternoon, highlighting the competitiveness of the Series this year.