By Alan Baldwin
GREATER NOIDA, India (Reuters) - Sebastian Vettel promised to treat the Indian Grand Prix like any other race, despite a fourth successive title beckoning, and lived up to his word in Friday practice with the sort of domination Formula One fans have come to expect.
Red Bull's 26-year-old German was fastest in both sessions, with Australian Mark Webber the closest to matching his team mate.
Despite Vettel's speed, it was not all smooth running for the champion who had a problem with the KERS energy recovery system and complained about the soft tires degrading too quickly.
"The tire has too much energy, just gives up. Same for everybody," he told reporters. "Sunday it could be a short stint on the option tire but usually the track rubbers in and things improve."
Ferrari's Fernando Alonso, the only man who can mathematically deny Vettel the title on Sunday, suffered a gearbox problem after six laps in the morning but was fifth fastest at the end of the day.
"The situation is not that different to recent races. We are a bit behind in performance terms and tomorrow we must try and get a good starting position to get away well in the race and make it to the podium," said the Spaniard.
Alonso has to finish in the top two on Sunday to have any chance of denying Vettel the title on Indian soil.
Vettel, who has a 90-point lead over the double champion with four races worth 100 points in total remaining, is the runaway favorite to win the race.
British bookmakers William Hill had him as 1/4 to win the race, 1/9 to take the title on Sunday (with odds of 5/1 on him not doing so) and 10/3 to win the rest of the season's races as well.
Such is Vettel's mastery of the Buddh International Circuit, a track swathed in a haze of pollution south of New Delhi, that he can boast of being top in every practice session held there since the opening day of the race's debut in 2011.
On Friday his best lap of one minute 25.722 seconds, in the afternoon after clocking 1:26.683 in the earlier session, made him the only driver below the 1:26 mark.
Webber, who is leaving the sport at the end of the season, was 0.188 seconds slower in the first practice and 0.281 off the pace in the afternoon when Frenchman Romain Grosjean was third with a best time nearly half a second slower than Vettel's.
Germany's Nico Rosberg was the best of the rest for Mercedes in the morning with a lap 0.216 off his compatriot's best effort.
"It seems that the main question this weekend is who can get third position behind the two Red Bulls, because they look pretty unstoppable at this circuit," said Rosberg.
"But I'm confident we will have a role to play in that battle tomorrow and on Sunday."
Vettel has won the previous two Indian Grands Prix from pole position as well as leading every competitive lap at the circuit.
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.
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. Hamilton was fourth in the afternoon.
"It's difficult to get the set-up right here and this circuit is pretty tough on the tires so I think everyone was struggling with the soft compound," said Hamilton. "Our car feels pretty good at this early stage but there are definitely some areas we can improve overnight."
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 returned for the second session, after Calado went off late in the morning.
The main incident in the afternoon was provided by Venezuelan Pastor Maldonado, whose Williams shed the front right wheelnut while out on track. He managed to nurse the car back to the pitlane entry, where he stopped.
(Additional reporting by Amlan Chakraborty; Editing by Clare Fallon)