Jean-Eric Vergne ended his first day of on-track running for Red Bull Racing on top of the timesheets in the Abu Dhabi young driver test.
The 21-year-old Frenchman, who finished second in Formula Renault 3.5 this year and is a regular simulator driver for the team, improved on his fastest time of the morning to set a best lap of 1m40.011s during the final hour of running.
This gave him an advantage of almost a second over Ferrari test driver Jules Bianchi, who focused on aerodynamic testing today.
Robert Wickens, who beat Vergne to the Formula Renault 3.5 crown in 2011, was third fastest on his first test for Renault, lapping just a tenth faster than best newcomer, Fabio Leimer, who adapted well to the step up to F1 machinery after racing in GP2 this year.
He ended the day sixth tenths of a second quicker than McLaren's Gary Paffett, who shared the day with Oliver Turvey.
Max Chilton, testing for Force India after previous straightline experience, jumped to sixth place with his best time in the final minute of the day to pip Valtteri Bottas by just one tenth of a second.
The Finn lost several hours of running with a gearbox problem that is still being investigated by Williams. The car returned to the track in the later afternoon after the gearbox was changed.
Despite this problem, he impressed the team with his approach and improved to a 1m43.118s in the closing stages of running. This put him ahead of McLaren's morning driver Turvey and Mercedes tester Sam Bird.
On his first full F1 test, Stefano Coletti (Scuderia Toro Rosso) finished 11th behind Team Lotus returnee Rodolfo Gonzalez.
GP2 race-winner Dani Clos returned to F1 testing action for the first time in two years, completing a day of running for HRT. He was just five hundredths of a second off Coletti's time.
Charles Pic, who is set to race for Virgin next year, had his first experience of Formula 1 with the team this afternoon. He took over the car from Adrian Quaife-Hobbs, who set his time during his 32 laps of running in the morning.
Pic completed a total of 30 laps, focusing on familiarising himself with the car and some short aero runs. He will return for a full day of running with the team tomorrow.
Pos Driver Team Time Laps 1. Jean-Eric Vergne Red Bull-Renault 1m40.011s 83 2. Jules Bianchi Ferrari 1m40.960s 85 3. Robert Wickens Renault 1m42.217s 78 4. Fabio Leimer Sauber-Ferrari 1m42.331s 67 5. Gary Paffett McLaren-Mercedes 1m42.912s 41 6. Max Chilton Force India-Mercedes 1m43.016s 81 7. Valtteri Bottas Williams-Cosworth 1m43.118s 71 8. Oliver Turvey McLaren-Mercedes 1m43.502s 35 9. Sam Bird Mercedes GP 1m43.548s 51 10. Rodolfo Gonzalez Lotus-Renault 1m44.022s 87 11. Stefano Coletti Toro Rosso-Ferrari 1m45.278s 87 12. Dani Clos HRT-Cosworth 1m45.329s 68 13. Charles Pic Virgin-Cosworth 1m46.930s 30 14. Adrian Quaife-Hobbs Virgin-Cosworth 1m47.292s 32 All Timing Unofficial