Kimi Raikkonen's Ferrari topped the timesheet in the third and final free practice session ahead of the Belgian Grand Prix, while Mercedes duo Lewis Hamilton and Nico Rosberg focused on their racing set-up.
The Mercedes pair were fastest in FP1 but Red Bull were quickest in the following session on Friday, with championship leader Hamilton down in 13th after having four new power unit elements installed.
The duo from the German squad were expected to return to the top of the timesheet ahead of qualifying on Saturday - Hamilton again taking a new set of four engine components - but were over half a second behind Raikkonen, whose time of one minute and 47.974 seconds was not beaten.
Daniel Ricciardo separated the Finn from his Ferrari team-mate Sebastian Vettel, who was 0.323secs back in third, while Valtteri Bottas went fourth fastest.
Hamilton and Rosberg, fifth and seventh respectively, focused their attention on longer stints on the soft tyre compound to fine-tune their race set-up before switching to the quickest supersofts.
Max Verstappen finished at the bottom of the board after encountering a gearbox issue which Red Bull will hope does not require a change and subsequent penalty.
An incident that saw Manor's Pascal Wehrlein run off track in an attempt to avoid Esteban Gutierrez's slow-running Hass is under investigation, while an alleged block of Vettel by Kevin Magnussen's Renault is also being looked at by race stewards.
Ferrari and Red Bull will be hoping to maintain their pace in qualifying and pip Rosberg to pole, with Hamilton expected to do minimal running as penalties will already see him start from the back of the grid.