Fernando Alonso underlined how much he wants to win his home Spanish Grand Prix with the fastest time in practice.
The world champion bounced back after being beaten by team-mate Lewis Hamilton in Friday's first session to dominate practice in the afternoon.
Alonso set a best lap of one minute 21.397 seconds to beat Hamilton, who was fifth, by 0.791secs.
The Renaults of Giancarlo Fisichella and Heikki Kovalainen were second and third, ahead of Ferrari's Felipe Massa.
Hamilton improved by only 0.1secs over his morning time, while Alonso found nearly 0.9secs.
606: DEBATE
Both drivers improved their times on their second series of laps, but this time Hamilton was just over 0.1secs faster than the world champion.
The 22-year-old improved his time again, by nearly 0.3secs on his third run, whereas Alonso did not go any faster, but the Spaniard was still clear of the Ferraris.
By the end of the afternoon Hamilton was sandwiched between the two Ferraris, with Kimi Raikkonen in sixth place, suggesting another close battle between F1's two dominant teams.
The pace of the Renaults appears not to be indicative of a major step forward after their disappointing start to the season, according to Fisichella.
"My feeling is that we are possibly a little bit closer to the cars in front of us," the Italian said, "even if we are clearly not fast enough to be second in the times on speed alone."
Kovalainen added: "The target has to be to qualify in the top 10 but, just like at the last three races, it is going to be tough."
Jenson Button continued to struggle in the Honda, managing only the 13th fastest time in the afternoon, just ahead of team-mate Rubens Barrichello.
Button was 10th fastest in the morning, when he was nearly half a second down on Anthony Davidson's Super Aguri, which is effectively Honda's 2006 car.
Button said: "We have made some small steps with the stability of the car since the last race but the outright pace has not yet improved a lot."
Davidson dropped to 20th in the second session.
Times from first practice at the Spanish Grand Prix:
1. Lewis Hamilton (GB) McLaren-Mercedes one minute 21.880 seconds
2. Fernando Alonso (Spa) McLaren-Mercedes 1:22.268
3. Kimi Raikkonen (Fin) Ferrari 1:22.291
4. Robert Kubica (Pol) BMW Sauber 1:22.446
5. Felipe Massa (Brz) Ferrari 1:22.565
6. Anthony Davidson (GB) Super Aguri-Honda 1:22.665
7. Jarno Trulli (Ita) Toyota 1:22.740
8. Ralf Schumacher (Ger) Toyota 1:22.843
9. Nico Rosberg (Ger) Williams-Toyota 1:23.048
10. Jenson Button (GB) Honda 1:23.114
11. Alexander Wurz (Aut) Williams-Toyota 1:23.131
12. Nick Heidfeld (Ger) BMW Sauber 1:23.170
13. Takuma Sato (Jpn) Super Aguri-Honda 1:23.316
14. Heikki Kovalainen (Fin) Renault 1:23.322
15. Giancarlo Fisichella (Ita) Renault 1:23.397
16. David Coulthard (GB) Red Bull-Renault 1:23.428
17. Mark Webber (Aus) Red Bull-Renault 1:23.444
18. Rubens Barrichello (Brz) Honda 1:23.479
19. Adrian Sutil (Ger) Spyker-Ferrari 1:23.954
20. Vitantonio Liuzzi (Ita) Toro Rosso-Ferrari 1:24.104
21. Scott Speed (USA) Toro Rosso-Ferrari 1:24.179
22. Christijan Albers (Ned) Spyker-Ferrari 1:24.396
Times from the second practice session:
1. Alonso 1:21.397
2. Fisichella 1:21.684
3. Kovalainen 1:21.966
4. Massa 1:22.048
5. Hamilton 1:22.188
6. Raikkonen 1:22.251
7. Rosberg 1:22.415
8. Heidfeld 1:22.543
9. Webber 1:22.589
10. Speed 1:22.617
11. Kubica 1:22.710
12. Coulthard 1:22.719
13 Button 1:22.808
14. Barrichello 1:22.926
15. Wurz 1:22.950
16. Liuzzi 1:23.143
17. Schumacher 1:23.219
18. Jarno Trulli, Italy, Toyota, 1:23.307
19 Sato 1:23.493
20. Davidson 1:23.497
21. Sutil 1:23.609
22. Albers 1:23.736
Follow live coverage of the Spainsh Grand Prix on BBC Five Live and this website. Qualifying starts at 1300 BST on Saturday, with the race at the same time on Sunday.