Renault's Fernando Alonso ended McLaren's domination by setting the pace in final practice for Sunday's Belgian Grand Prix.
Alonso is odds-on to win the drivers' championship
Kimi Raikkonen had been setting the standard but Alonso raised his game to clock one minute 46.307 seconds.
Raikkonen, winner in Spa last year and more than a second quicker than his rival in the first session of the day, was 0.334 seconds slower.
He is 27 points adrift of Alonso in the drivers' table with four races left.
Alonso, 24, will become F1's youngest champion if he scores four points more than the Finn on Sunday.
McLaren had another good morning with Colombian Juan Pablo Montoya second and fourth in the two sessions.
And Toyota's Jarno Trulli was third on the timesheets.
Seven-times champion Michael Schumacher, mathematically ruled out of the championship after scoring no points in the last two races, was only ninth in the final session on his favourite circuit.
The Ferrari ace won his seventh title at Spa last year. The circuit was also the venue of his Formula One debut in 1991 and his first Grand Prix win in 1992.
1. Fernando Alonso (Spa) Renault 1:46.307
2. Kimi Raikkonen
(Fin) McLaren-Mercedes 1:46.641
3. Jarno Trulli (Ita) Toyota
4. Juan Pablo Montoya (Col) McLaren-Mercedes 1:46.858
Giancarlo Fisichella (Ita) Renault 1:47.049
6. Ralf Schumacher
(Ger) Toyota 1:47.054
7. Jenson Button (GB) BAR-Honda 1:47.419
Takuma Sato (Jpn) BAR-Honda 1:47.507
9. Michael Schumacher (Ger)
10. Rubens Barrichello (Bra) Ferrari 1:47.991