Lando Norris edged out new world champion Kimi Antonelli to top the opening practice session at the São Paulo Grand Prix.
McLaren have brought a significant upgrade package to Interlagos, in a bid to end the season strongly and put its car in a positive place for the start of next year.
Norris has shown promising pace in flashes across recent races but has been unable to string laps together consistently. He found his stride in the weekend's opening running, pipping Antonelli by 0.082 seconds.
Antonelli replaced Norris as champion by becoming F1's youngest title-winner last weekend, clinching it with third place in Mexico.
His Mercedes teammate George Russell, now down to fourth in the championship, will start this weekend's race with a five-place grid drop due to an engine change.
The British driver was fifth fastest. Mercedes can wrap up the constructors' championship this weekend if they outscore Ferrari by three points.
Max Verstappen -- winner of three of the last four races -- was third-fastest.
Charles Leclerc was not driving in FP1. The Monégasque has been back home for the birth of his first child, while Lewis Hamilton continued the criticism of his Ferrari teammate on Thursday.
Hamilton was furious with Leclerc for a lap-one move in Mexico last weekend, questioning the 29-year-old's mentality.
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- Valtteri Bottas 'surprised' by whispers of Cadillac exit
- George Russell breaks silence on swift Mexico City GP exit: 'Needed to get out of there'
The seven-time world champion vowed not to be silenced as he arrived in Brazil, suggesting Leclerc races against him differently to how he approaches other drivers.
Hamilton was fourth in FP1. Leclerc will be in action for second practice later on Friday.
The weekend's first running was red-flagged 13 minutes in when British teenager Freddie Slater came to a halt.
Slater sat cross-armed by the side of the track as his Audi was lifted away -- his running caught short for the second week in a row.
Rafael Câmara finished 18th on his F1 debut for Haas. The Brazilian, current F2 leader who will drive full-time for the American side next season, has been parachuted in after Frenchman Esteban Ocon was removed from the team.
Ocon admitted to a disagreement with the team during last weekend's round in Mexico, where he was withdrawn midway through, and Haas have confirmed he will not drive for them again.
Gabriele Minì, one of six rookie drivers taking part in FP1, was an impressive seventh for Alpine.