Valtteri Bottas upheld Mercedes dominance in free practice at Monza, the Finn clocking in fastest in the final session before this afternoon's qualifying.
But it wasn't a Mercedes clean sweep as a late effort by McLaren boys Carlos Sainz and Lando Norris positioned the pair second and third behind Bottas.
Daniel Ricciardo was also among the top four thanks to a brilliant lap, but the Renault driver immediately encountered an issue that forced him to park his car in the closing stages of FP3.
Lewis Hamilton concluded the session fifth, just edging Red Bull's Max Verstappen.
Monza's parklands were basking once again in warm temperatures and resting under the sun, perfect conditions therefore for teams to resume work ahead of this afternoon's all-important qualifying session.
Italy's second favourite team, Alfa Romeo Racing, sent its drivers out first for the unavoidable installation laps, the duo followed by a Haas pair and Norris.
Action remained lethargic for the first twenty minutes until Sainz finally put a time on the board, inciting others to join the action.
While the FIA has established a minimum lap time to avoid drivers slowing excessively and jockeying for position before a hot lap, there were still signs of congestion out on the track, with Charles Leclerc impeding an irritated Norris on the entry to Parabolica.
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Eventually however, the front-runners got down to business, with a fast lap by the medium-shod Verstappen topping the timing screen from Bottas, Hamilton Renault' Esteban Ocon and racing Point's Sergio Perez.
Meanwhile, languishing well down the order, Leclerc and Vettel continued to struggle, the Monegasque approximately 1.3s off the pace.
As the session entered the final 15 minutes, Hamilton and Bottas exited the Mercedes garage each on a set of Pirelli softs, likely to gauge their qualifying pace.
The Finn laid down a 1m20.089s that shadowed Verstappen by over three tenths, the Mercedes appearing absolutely on the edge on the exit of Parabolica.
Hamilton could not beat his teammate's prime effort, clocking on 0.35s behind.
But Ricciardo's flyer was good enough for an impressive third. However, the Aussie was forced to pull over to the side of the track, the victim of an apparent engine issue, which also brought out the red flag.
With just two hours to spare before qualifying, the Renault mechanics could be facing a race against the clock to prep the R.S.20 for the afternoon session.
Just before Ricciardo's stoppage, Norris popped up out of nowhere to slot himself into P2 behind Bottas and ahead of Ricciardo and Hamilton.
In the final minutes of the session, Sainz confirmed McLaren's pace, just edging his teammate for second, with Ricciardo, Hamilton and Verstappen completing the top six.
It was a messy end to FP3 however, with Hamilton nearly plowing into the back of a slow-moving Haas car on the approach to Parabolica.
A sign of things to come in qualifying? Hopefully not…
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