Red Bull's Sebastian Vettel set the pace in first practice at the Indian Grand Prix.
Vettel headed team-mate Mark Webber by 0.188 seconds, getting his preparations for the race in which he hopes to clinch his fourth title off to a perfect start.
Mercedes driver Nico Rosberg was third ahead of Lotus's Romain Grosjean.
Ferrari's Fernando Alonso, the only other man who can still win the title, suffered a gearbox problem.
The Spaniard ended up 12th fastest, managing just six laps before being forced to abandon the session.
Alonso must score at least 16 points more than Vettel this weekend to prolong the championship but will be out of contention if the German finishes fifth or higher.
Vettel has won the last five races and the first practice session underlined that he is a strong favourite to make it six in a row.
Alonso said: "It is a matter of time when he will get the championship. I am sure he will try to win the remaining four races and he has the potential to win all four.
"We will try to be as close to him as possible and try to fight for the podium but I don't think Sebastian's approach will change our race."
Mercedes' Lewis Hamilton was fifth quickest, ahead of the McLarens of Jenson Button and Sergio Perez.
Alonso's team-mate Felipe Massa was only ninth fastest, just over a second off the pace, and ahead of Sauber's Nico Hulkenberg, Williams's Valtteri Bottas and Toro Rosso's Jean-Eric Vergne.
Lotus's Kimi Raikkonen, who has admitted he needs to improve his form in qualifying, was only 17th.
There were spins for Williams's Pastor Maldonado and Force India reserve driver James Calado at the tricky Turn Five as they came to terms with the dusty, rarely used track surface. Calado ended the session 18th.
BBC F1 technical analyst Gary Anderson said: "The Red Bulls look very strong - Webber did his best time on his 15th lap, so they clearly can look after their tyres as well."