Kimi Raikkonen out-paced Daniel Ricciardo and Ferrari team-mate Sebastian Vettel to top the timings in the third and final practice session ahead of the Belgian GP, but there were problems for Friday pace-setter Max Verstappen.
Raikkonen clocked a 1:47.974 to finish two tenths faster than Ricciardo, with Vettel a tenth a further back in third and Nico Rosberg well off the pace in seventh, although it is suspected that Mercedes were running with more fuel on board.
Valtteri Bottas was an encouraging fourth for Williams, who had languished at the lower end of the midfield in FP2, while the penalised Lewis Hamilton slotted into fifth place with a late lap on the supersoft tyres.
The Briton again spent much of the session focusing on long runs, but did struggle a touch, suffering a number of lock-ups into the Bus Stop chicane.
Nico Hulkenberg wound up sixth fastest for Force India ahead of the aforementioned Rosberg, with Felipe Massa, Sergio Perez and Romain Grosjean rounding out the top ten.
Fernando Alonso was just outside the top ten for McLaren as Esteban Gutierrez took 12th and Jenson Button finished the session 13th.
Kevin Magnussen improved to P14 in the Renault after struggling on Friday, with Pascal Wehrlein comfortably ahead of team-mate Esteban Ocon once more, but only after a near miss with Gutierrez on the run to the Kemmel Straight, which left the young German incensed.
Toro Rosso look set for a difficult weekend as Carlos Sainz and Daniil Kvyat managed only sixteenth and seventeenth respectively, a few tenths clear of Jolyon Palmer and Felipe Nasr.
Debutant Ocon was 20th as he prepares for his first F1 qualifying session, while Marcus Ericsson propped up the field after Max Verstappen failed to set a time, sidelined for much of the session by a gearbox sensor issue which could see the Dutchman hit with a grid penalty.