Red Bull's Max Verstappen headed Ferrari's Sebastian Vettel and Lewis Hamilton's Mercedes in first practice at the Brazilian Grand Prix.
Just 0.096 seconds separated the three drivers around one of the shortest tracks on the calendar.
Red Bull's Daniel Ricciardo was fourth, 0.384secs off his team-mate, ahead of Ferrari's Kimi Raikkonen and the second Mercedes of Valtteri Bottas.
Mercedes can win a fifth consecutive constructors' title on Sunday.
To do so, they simply have to ensure Ferrari do not score 12 more points than them. Hamilton clinched a fifth drivers' title at the last race in Mexico.
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Hamilton is hoping he can bounce back to competitiveness this weekend, after two races in which Mercedes have struggled for pace.
The world champion said Mercedes had not yet got to the bottom of their problems, particularly in Mexico, where the issue in the race was a lack of tyre temperature, which led to excessive tyre damage.
"It is not always the case you find all the solutions," Hamilton said, "so I am confident everyone has worked as hard as they can to rectify it and push forward but it might take this race and even the next race before we fully understand it.
Hamilton has also said he wants to break a run in which he has failed to win another race after clinching the title in seasons in which he became champion early.
Best of the rest were the Haas drivers Romain Grosjean and Kevin Magnussen, followed by Sauber's Charles Leclerc and the Force India of Esteban Ocon.
Briton Lando Norris, running in first practice in Fernando Alonso's McLaren in preparation for his debut next season, was 16th fastest.
Regular McLaren racer Stoffel Vandoorne, who Norris is replacing in 2019, was 19th, using the hardest 'medium' tyre, while Norris was on the quicker 'soft' tyre.