Ferrari duo set the pace
McLarens in the shade at Spa
Felipe Massa led a Ferrari one-two as he edged out team-mate Kimi Raikkonen in first practice at Spa.
The two Ferraris had the better of their McLaren rivals as they traded blows throughout practice with Massa eventually finishing on top with a 1:47.284.
That put him 0.339s ahead of Raikkonen while the McLarens of Lewis Hamilton and Heikki Kovalainen slotted in behind.
Massa has been the Formula One force of late, with the Brazilian taking the chequered flag in the European Grand Prix in Valencia 12 days ago.
After Raikkonen suffered from engine trouble in Valencia, Ferrari bosses are naturally hoping they have solved the problem and they will be trouble-free this weekend.
There were certainly no issues during the opening 90-minute session at a Spa track a world removed from the processional Hungaroring and Valencia Street Circuit.
Winding its way through the Ardennes forest for 4.35 miles, Massa was comfortably quickest, setting fastest lap after fastest lap in the closing stages, leaving Raikkonen and Lewis Hamilton trailing.
Hamilton may currently hold a six-point cushion over Massa and 13 to Raikkonen, but he can expect that to be cut on Sunday if such a performance is repeated in the race.
The Ferraris have generally performed better in hotter conditions, yet although temperatures were around 15 degrees centigrade cooler than in Budapest and Valencia, Massa was out on his own.
By the close, the 27-year-old's lap of one minute 47.284 seconds was 0.339secs quicker than Raikkonen, with Hamilton 0.594secs adrift.
McLaren team-mate Heikki Kovalainen was in close attendance in fourth, with Renault's Fernando Alonso fifth, and the only other driver to finish within a second of Massa.
The Red Bull family occupied the next three places, with Racing's Mark Webber followed by the Toro Rosso duo of Sebastien Bourdais and Sebastian Vettel.
Toyota's Timo Glock and the second Renault of Nelson Piquet rounded out the top 10, with the latter a staggering 1.784secs behind Massa.
David Coulthard was 15th for Red Bull, with the rear of the field disappointingly brought up by Honda duo Jenson Button and Rubens Barrichello, both an embarrassing three seconds down.
01 F. Massa Ferrari 1:47.284 25 laps
02 K. Räikkönen Ferrari 1:47.623 25 laps
03 L. Hamilton McLaren 1:47.878 27 laps
04 H. Kovalainen McLaren 1:47.932 24 laps
05 F. Alonso Renault 1:48.104 25 laps
06 M. Webber Red Bull 1:48.428 28 laps
07 S. Bourdais Scuderia Toro Rosso 1:48.557 30 laps
08 S. Vettel Scuderia Toro Rosso 1:48.958 24 laps
09 T. Glock Toyota 1:48.997 26 laps
10 N. Piquet jr. Renault 1:49.068 24 laps
11 R. Kubica BMW 1:49.139 25 laps
12 N. Heidfeld BMW 1:49.185 26 laps
13 N. Rosberg Williams 1:49.611 30 laps
14 J. Trulli Toyota 1:49.625 14 laps
15 D. Coulthard Red Bull 1:49.849 18 laps
16 G. Fisichella Force India F1 1:49.986 27 laps
17 A. Sutil Force India F1 1:50.117 19 laps
18 K. Nakajima Williams 1:50.125 30 laps
19 J. Button Honda 1:50.464 24 laps
20 R. Barrichello Honda 1:50.905 25 laps