The session was barely 10 minutes old when Romain Grosjean caused an early Virtual Safety Car after spinning his Haas off into the gravel at the Ascari chicane. When the action resumed, Hamilton and Rosberg set the pace with 1m 22.856s and 1m 23.333s respectively on softs until Vettel split them with 1m 23.312s – but the German was on supersofts.
As Kimi Raikkonen was fourth in the other Ferrari on 1m 23.490s, Daniel Ricciardo headed Red Bull partner Max Verstappen in fifth and sixth, on 1m 23.709s and 1m 23.740s, though the Dutchman - who’d earlier appeared to impede Rosberg on a quick lap - lost some time going wide at Ascari, passing Kevin Magnussen’s slowly moving Renault.
When they made their supersoft runs, Hamilton lapped in a scorching 1m 22.008s, with Rosberg on 1m 22.401s. Vettel improved to 1m 22.946s, and Raikkonen to 1m 23.149s, but Williams jumped ahead of Red Bull with Bottas on 1m 23.500s, and Felipe Massa on 1m 23.647s.
Sergio Perez took ninth for Force India on 1m 23.917s as Esteban Gutierrez completed the top 10 with 1m 24.034s for Haas. Behind the Mexican, just 0.897s covered Force India's Nico Hulkenberg in 11th on 1m 24.041s and Manor rookie Esteban Ocon in 22nd on 1m 24.938s.
The only other incident of note occurred in the latter stages of the session as Jolyon Palmer’s Renault ran wide through the gravel at Parabolica before recovering to the track.