Lewis Hamilton has the recent edge on Mercedes teammate Nico Rosberg, winning the last two Formula One races in Mexico and the United States.
The Englishman had it again Friday in both practices for the Brazilian Grand Prix, each time finding just a sliver of extra pace to nip Rosberg.
Hamilton needs a victory on Sunday to push the season-title chase to the last race in two weeks in Abu Dhabi.
"It's been a good day," Hamilton said. "It's pretty tough out here physically right now with the heat as high as it is. We can be happy with the start we made today."
For his part, Rosberg can claim his first Formula One title if he wins on Sunday, which would deprive Hamilton of a chance for his fourth driver's title.
Rosberg leads Hamilton by 19 points in the season standings through 19 of 21 races. The German also complained about the heat as Brazil moves into its summer months.
"Strategy-wise it won't be straightforward for the race," Rosberg said. "But, again, it's meant to get quite a lot colder so we could see something completely different on Sunday."
The track was dry on Friday and should be in qualifying on Saturday. But rain is in the forecast for Sunday, which could cause havoc and upsets.
The Interlagos circuit has a history of wet races and shocking finishes.
"There's some unpredictable weather forecast over the next few days, so opportunities can hopefully present themselves to put up a bit of a challenge," said Christian Horner, team principal for Red Bull, which has been Mercedes' No. 1 rival all season.
To be fair, Hamilton might be leading the standings were it not for the Malaysian Grand Prix in October. His engine caught fire near the end of the race, a race he was leading easily. That cost him 25 points and he's been chasing ever since.
Hamilton was 0.230 seconds faster than Rosberg in the first practice session, and just a tiny sliver faster in the second – 0.030 – on the hilly track south of Sao Paulo's downtown area.
"This circuit is renowned for throwing jokers into the pack," Paddy Lowe, Mercedes technical director said. "So we take nothing for granted heading into the weekend."