Nick Heidfeld provided a welcome, if belated and probably meaningless, boost to the BMW
Sauber team by posting the fastest time of third and final practice ahead of qualifying for Sunday's Belgian Grand Prix, as the title contenders struggled to make the top ten.
While strategy always plays a big part in deciding the order of Saturday morning's hour-long session, the top half of the order bore little resemblance to that expected when things get serious later in the day, with only Jenson Button
of the championship hopefuls featuring - and that after languishing well down the timesheets for much of the morning.
While the Briton again battled against cool temperatures - weaving his Brawn down Spa's lengthy straights in an attempt to warm his tyres - team-mate Rubens Barrichello
ended the session only 16th fastest, two spots behind Red Bull's Sebastian Vettel, but comfortably clear of Mark Webber, who failed to post a time after sitting out much of the first half of the session and then succumbing to another engine problem on his RB5 that will necessitate a change of powerplant before qualifying.
At the sharp end, Heidfeld vaulted to top spot in the final few minutes, posting a 1min 45.388secs best - comfortably better than Friday's benchmark - that edged Toyota's Jarno Trulli
into second, with Adrian Sutil
an equally surprising fixture in third for Force India. Renault
rookie Romain Grosjean
was fourth fastest, ahead of Timo Glock, Robert Kubica
- ensuring Toyota
both had two cars in the top six.
The top nine, rounded out by Friday pacesetter Lewis Hamilton, were all within a second of Heidfeld's target time, with the next four drivers, book-ended by the second McLaren
of Heikki Kovalainen, within 1.1secs. The slowest runner, Kazuki Nakajima, was just 1.6secs off the pace.