Adrian Sutil continued Force India's excellent form by topping the second practice session at Monza.
The two Renaults completed the top three, with the inexperienced Romain Grosjean impressively beating his double world champion teammate Fernando Alonso to second place as the team remained in the spotlight off-track amid the scandal over last year's Singapore Grand Prix.
Sutil sat out the first half an hour while Force India completed an engine change, but once he hit the track the German immediately launched into a rapid series of laps that put him straight into the top five and drew him ever closer to early pace-setter Nick Heidfeld (BMW).
While Sutil was still running on hard tires, Heidfeld had set his time on softs - and it was when the Force India man switched the softer tires 15 minutes later that he managed to knock his compatriot off the top spot.
It was only in the final five minutes that Sutil came under threat, as a sensational effort from Grosjean saw Renault's rookie go quickest. Alonso came through to take second moments later.
Sutil failed to improve with his initial response, but split the Renaults next time around. Then he dug even deeper and came up with a 1m23.924s to secure first position by 0.239sec.
The Renaults held on to second and third as Heikki Kovalainen's late improvement only got the McLaren into fourth place.
BMW remained competitive, with Robert Kubica and Heidfeld taking fifth and seventh, split by Toyota's Timo Glock, who fared much better than in the morning.
Kimi Raikkonen was eighth, while teammate Giancarlo Fisichella was slowest of all in the second Ferrari - although he was a respectable 0.8sec down on the Finn.
Kazuki Nakajima escaped a wild high-speed trip through the Parabolica gravel to take ninth for Williams. Toro Rosso's Sebastien Buemi completed a good day by finishing the afternoon in 10th, ahead of morning pacesetter Lewis Hamilton (McLaren) and Sutil's new team-mate Tonio Liuzzi.
The Red Bulls and Brawns were all in the midfield, with Mark Webber the best of the quartet in 14th despite an electrical problem sidelining him for a while. Championship leader Jenson Button only managed to beat Fisichella, taking a worrying 19th.
Pos Driver Team Time Laps
1. Sutil Force India-Mercedes (B) 1:23.924 28
2. Grosjean Renault (B) 1:24.163 + 0.239 31
3. Alonso Renault (B) 1:24.297 + 0.373 35
4. Kovalainen McLaren-Mercedes (B) 1:24.482 + 0.558 41
5. Kubica BMW-Sauber (B) 1:24.622 + 0.698 40
6. Glock Toyota (B) 1:24.634 + 0.710 36
7. Heidfeld BMW-Sauber (B) 1:24.693 + 0.769 34
8. Raikkonen Ferrari (B) 1:24.796 + 0.872 39
9. Nakajima Williams-Toyota (B) 1:24.799 + 0.875 36
10. Buemi Toro Rosso-Ferrari (B) 1:24.884 + 0.960 44
11. Hamilton McLaren-Mercedes (B) 1:24.902 + 0.978 32
12. Liuzzi Force India-Mercedes (B) 1:24.921 + 0.997 39
13. Trulli Toyota (B) 1:24.967 + 1.043 40
14. Webber Red Bull-Renault (B) 1:24.979 + 1.055 25
15. Alguersuari Toro Rosso-Ferrari (B) 1:25.003 + 1.079 34
16. Barrichello Brawn-Mercedes (B) 1:25.140 + 1.216 35
17. Rosberg Williams-Toyota (B) 1:25.215 + 1.291 38
18. Vettel Red Bull-Renault (B) 1:25.386 + 1.462 27
19. Button Brawn-Mercedes (B) 1:25.424 + 1.500 32
20. Fisichella Ferrari (B) 1:25.543 + 1.619 36
All Timing Unofficial