Sebastian Vettel gears up as Formula One season begins

Red Bull's Sebastien Vettel has swept four straight Formula One titles but a comprehensive shift in technical requirements threatens to leave him trailing when the season starts on Sunday.

A disastrous pre-season has left even the upbeat Vettel fearing the worst at this week's Australian Grand Prix, after the decade's dominant driver was just 18th fastest over four days of testing in Bahrain.

"First of all, just getting to the finish would be a success," the 26-year-old German grumbled to Servus TV. "If half the drivers fail to finish, then maybe we could take a few points." (F1 2014 season: New engines, fuel limit head list of changes)

Chief among Red Bull's problems is the change from 2.4-litre V8 engines, whose distinctive high-pitched whine has been the soundtrack of Formula One, to turbo-charged 1.6-litre V6s.

In another nod to eco-friendliness, cars are limited to 100 kilos (220 pounds, about 135 litres) of fuel per race, about two-thirds of the biggest loads carried previously.

While all teams are grappling with the new rules, the overheating Red Bull has been one of the worst affected, logging just 1,705 kilometres (1,060 miles) in testing while Mercedes and Williams clocked nearly 5,000km.

Lotus, which like Red Bull, Toro Rosso and Caterham have Renault engines, are also struggling badly, with one official saying they would need luck just to cross the finish line at Melbourne's Albert Park.

But the predicament is more serious for Red Bull as it threatens to end their era of dominance and torpedo Vettel's bid to match Michael Schumacher by winning five titles in a row.

Vettel was initially a fierce opponent of another innovation this year: the controversial decision, aimed at prolonging the title race, to award double points at the final race in Abu Dhabi.

But double points -- introduced after Vettel cruised to his fourth consecutive title, with three races to go -- could come to the German's rescue if he gets off to a slow start this season.

Mercedes' Lewis Hamilton and a resurgent Williams, who last won drivers' and constructors' championships in 1997, will hope to make the early running after a positive session in Bahrain.

Felipe Massa, discarded by Ferrari, topped the aggregate timings for Williams, ahead of Hamilton and Mercedes team-mate Nico Rosberg, with Valtteri Bottas fourth in the second Williams.

"I think we're as ready as we can be for Melbourne and I'm more fired up than ever," said Hamilton, the 2008 world champion, according to the official F1 website.

"With all the changes within the sport and the hard work that's been going on within the team, I believe this can be our year to really show what we're capable of."

McLaren, who have 20 drivers and constructors titles but failed to reach the podium last year, will expect a big improvement after part-owner Ron Dennis returned to a more hands-on role.

McLaren, described by the bullish Dennis as Formula One's "Manchester United", also have a new driver with Danish rookie Kevin Magnussen partnering Jenson Button.

But the most closely watched pairing will be Fernando Alonso and Kimi Raikkonen, after Ferrari took a gamble in bringing two strong-willed former world champions into the same garage.

Sweden's Marcus Ericsson will make his debut with Caterham, while Russia's Daniil Kvyat is another rookie this year driving for Toro Rosso after Australian Daniel Ricciardo joined Vettel at Red Bull.

The 19-race season will make a new stop in Russia's Sochi and will return to Austria, Red Bull's home country, for the first time in 11 years -- giving the champions even more incentive to fix their current problems.