Valtteri Bottas and Lewis Hamilton set the pace in practice for the Brazilian Grand Prix on Friday, keeping Mercedes with the edge in the fight for the Formula One constructors' championship.
Bottas edged his Mercedes teammate on a warmer Interlagos track than the expected for the rest of the weekend. The Finnish driver had a lap of 1 minute, 08.846 seconds in the second practice session at the Sao Paulo circuit, with world champion Hamilton only 0.003 seconds behind.
Ferrari's Sebastian Vettel finished third, 0.073 seconds from Bottas. The Red Bulls of Daniel Ricciardo and Max Verstappen ended in fourth and fifth places, respectively, and Vettel's teammate Kimi Raikkonen was sixth.
Mercedes leads Ferrari in the constructor's championship by 55 points.
Bottas could not say what made the small difference between him and five-time champion Hamilton. He insisted the two Mercedes will have to improve to secure the constructors' title.
"We can't be feeling satisfied going to the hotel tonight, everyone will be working," said Bottas, currently fourth in the drivers' championship. "It is a short track, so the margin (for improvement) is small."
Hamilton said he expects the biggest challenge coming from Ferrari, not Red Bull. He said "the car is feeling better than in Mexico," where he secured his title two weeks ago.
"We got through everything we needed to," he said. "We just need to keep working on it."
Vettel said his performance was troubled by a screw that fell between his legs during the afternoon session. "We found it in the end!" the four-time champion said. "We still have to improve the car because it doesn't feel good yet. If we get the balance in the window tomorrow, then it can be tight (against Mercedes)."
The German driver is under pressure to deliver good performances in Brazil and in the season-ending Abu Dhabi GP after a series of mistakes that left him out of contention for the title.
Red Bull's Verstappen led the first practice session on Friday, with Vettel and Hamilton close behind.
Ricciardo, who was fourth in both sessions, was handed a five-place grid penalty after Red Bull had to replace his turbocharger for the sixth time this season.
The Australian driver, who was on pole position in Mexico, also started from the back because of penalties in Italy and Russia.
"It sounds really simple and silly, but bad luck really is the best term I can use," Ricciardo said.
The second session was stopped after nine minutes because Renault's Nico Hulkenberg crashed entering the front stretch. The German driver was not injured but the car was badly damaged.