Seven-time world champion Michael Schumacher continued to steal the show at Barcelona, where he finished on top of the times for the second day in a row.
Schumacher's best time of 1:21.486 put him nearly four tenths of a second ahead of McLaren's test driver Pedro de la Rosa, second fastest today.
Schumacher was joined at Ferrari by Brazilian Felipe Massa, who took over from test driver Luca Badoer. Massa finished as fourth quickest, nearly six tenths behind Schumacher.
The German driver focused again on working with the electronics for the 2008 season, testing without driving aids.
The Ferraris were split by Renault's Heikki Kovalainen, while Briton Gary Paffett completed the top five with the second McLaren.
Williams drivers Nico Rosberg and Kazuki Nakajima continued making progress for the British squad, with Rosberg posting the sixth fastest time of the day, three places ahead of his Japanese teammate.
David Coulthard was seventh fastest for the Red Bull Racing team after a more productive day than yesterday. The Scot worked alongside Karun Chandhok, who had a positive day and finished as 11th quickest as he worked on the 2008 electrical systems.
Jarno Trulli and Franck Montagny were again the men in charge of testing duties for the Toyota team. The Italian evaluated new parts for 2008 while the Frenchman continued work won the standard ECU to be used next season.
They caused a red flag each when they spun on track, with Montagny causing damage to the rear of his car after hitting the wall at turn 13.
"Today was a smooth day for me," said Trulli. "Again I enjoyed myself driving without traction control. I must say we had a very positive and productive day.
"We were testing several things which made our car quicker. I lost part of the morning because I went off into the gravel but apart from that we got the best out of our day. We have had some good and clear indications for next year regarding car development so I am very happy."
Jenson Button was joined by Italian Luca Filippi, who made his debut in a Formula One car as part of Honda's young driver programme. The GP2 racer, who will be replaced tomorrow by Mike Conway, finished as 16th quickest.
The Force India squad had three drivers on track, with Adrian Sutil being partnered by Vitantonio Liuzzi and Christian Klien, as the team evaluate drivers for the 2008 season.
Austrian Klien drove in the morning and was the fastest of the three cars, while Liuzzi took to the track in the afternoon and finished at the bottom of the times.
Pos Driver Team Time Laps 1. M.Schumacher Ferrari (B) 1:21.486 90 2. de la Rosa McLaren-Mercedes (B) 1:21.857 60 3. Kovalainen Renault (B) 1:21.894 65 4. Massa Ferrari (B) 1:22.044 56 5. Paffett McLaren-Mercedes (B) 1:22.293 57 6. Rosberg Williams-Toyota (B) 1:22.333 64 7. Coulthard Red Bull-Renault (B) 1:22.555 74 8. Heidfeld BMW-Sauber (B) 1:22.946 102 9. Nakajima Williams-Toyota (B) 1:23.031 77 10. Vettel Toro Rosso-Ferrari (B) 1:23.187 74 11. Chandhok Red Bull-Renault (B) 1:23.255 57 12. Button Honda (B) 1:23.358 79 13. Trulli Toyota (B) 1:23.465 54 14. Kubica BMW-Sauber (B) 1:23.488 37 15. Davidson Super Aguri-Honda (B) 1:23.547 80 16. Filippi Honda (B) 1:23.596 74 17. Bourdais Toro Rosso-Ferrari (B) 1:23.753 72 18. Montagny Toyota (B) 1:23.977 45 19. Klien Force India-Ferrari (B) 1:24.446 56 20. Sutil Force India-Ferrari (B) 1:24.537 105 21. Liuzzi Force India-Ferrari (B) 1:24.555 55 All Timing Unofficial