Sebastian Vettel led a Red Bull one-two in Friday's first free practice for an Indian Grand Prix that looks sure to secure the German a fourth successive Formula One title.
The 26-year-old German lapped the hazy Buddh International Circuit near New Delhi with a best lap of one minute 26.683 seconds.
Australian teammate Mark Webber, who is leaving the sport at the end of the season, was 0.188 seconds slower with Germany's Nico Rosberg the best of the rest for Mercedes with a lap 0.216 off his compatriot's pace.
Ferrari's Fernando Alonso, the only man who can mathematically deny Vettel the title on Sunday, suffered a gearbox problem after six laps and ended up with only the 12th fastest time.
Vettel, who has a 90 point lead over Alonso with four races worth 100 points in total remaining, has won the previous two Indian Grands Prix from pole position and has also led every competitive lap to date at the circuit.
The German was fastest in every practice session in India last year and made a perfect start to a weekend that he says he will treat like any other despite a place in history beckoning.
He will be the first Formula One driver to win his first four titles in a row, as well as the youngest quadruple champion.
Only seven times champion Michael Schumacher and the late Argentine Juan Manuel Fangio have won four successive titles since the championship started in 1950. Frenchman Alain Prost is the sport's only other four times champion.
Frenchman Romain Grosjean was fourth for Lotus in the opening session, ahead of Lewis Hamilton's Mercedes, with the McLarens of Jenson Button and Sergio Perez sixth and seventh on the timesheets.
British reserve James Calado replaced compatriot Paul Di Resta in the Force India for the opening session after the team said the regular race driver had not felt 100 percent on Thursday.
Di Resta is expected to return for the second session, with Calado spinning off late in the morning.
Image: Sebastian Vettel of Germany and Infiniti Red Bull Racing prepares to drive during practice for the Indian Formula One Grand Prix at Buddh International Circuit on Friday
Photograph: Mark Thompson/Getty Images