challenge from Ferrari, McLaren and Mercedes in 2013.
The German Red Bull driver was crowned the youngest three-time champion in 2012, grabbing the championship from Ferrari's Fernando Alonso by just three points in a breath-taking season-finale in Brazil after a roller-coaster campaign.
Vettel and Red Bull, whose lacklustre performance in pre-season winter testing was masked by sleight of hand fuelling to keep rivals guessing, will start the 19-race campaign as favourites.
Ferrari and McLaren will, as always, be closely tucked in, but Mercedes, with a bank-busting budget and with Lewis Hamilton having replaced Michael Schumacher, are widely-expected to smash through the three-team dominance.
Hamilton and Nico Rosberg, who consistently out-paced the ageing Schumacher in 2012, set the fastest times in testing in Barcelona, while former champions Alonso and McLaren's Jenson Button, were just off their shoulders.
Hamilton, the 2008 champion, insists his first year with the German giants will be a learning curve and that teams' strengths and weaknesses will not be apparent until the season-opener in Melbourne on March 17.
"I don't think there are any expectations," Hamilton told autosport.com.
"If anything, I feel like I have a free ticket. It's a year where we know we may not have the best package, but it's a challenge for me.
"I think the pressure is more on the other guys, who had great cars and were evolved into this year's car. They have the pressure to go and compete and perform. For us, we only have everything to gain."
Vettel, looking to emulate Juan Manuel Fangio and Schumacher as a four-in-a-row champion, was only eighth fastest in testing at Barcelona last weekend. His test, as well as that of teammate Mark Webber, saw the Red Bulls run full of fuel and with 2012 having seen a dip in their dominance -- seven wins compared to 11 the year before -- Vettel is keeping his feet on the ground.
"We're in good enough shape I think. Overall testing has been good for us and we didn't have too many problems," said the German.
"But if you sum up all three tests I think all the teams were linked in to what the tyres could do and at times it was extremely difficult to read the set-up changes.
"I'm looking forward to Melbourne now and can't wait for the racing to begin."
The starting grid in Australia will see 11 teams and not the 12 of a year ago after Spanish strugglers HRT went to the wall of the global economic crisis.
Reflecting the sobre financial climate will be the appearance of more pay-drivers, those men fortunate enough to have courted wealthy patrons or been born into moneyed circumstances.
Britain's Max Chilton, whose father is believed to have banked around ?70 million when he sold his stake in an insurance company, will debut for Marussia.
At Caterham, France's Charles Pic, whose mother built up a wealthy portfolio through a French trucking operation, has switched from Marussia where he finished in 21st place last year.
Esteban Gutierrez moves into a Sauber seat vacated by Sergio Perez -- who has replaced Hamilton at McLaren -- helped by Mexican communications giant Telmex.
Also making their debut in 2013 will be Finland's Valtteri Bottas in a Williams, Dutch driver Giedo van der Garde at Caterham and France's Jules Bianchi, a late addition for Marussia.
Making way are the likes of Timo Glock, Bruno Senna, Heikki Kovalainen and flamboyant Japanese driver Kamui Kobayashi.
The season will comprise just the 19 races after the FIA, which governs the sport, was unable to come up with a suitable venue for the July 21 slot left empty by the cancellation of the New Jersey grand prix.
All eyes on Hamilton
Lewis Hamilton handed Formula One a compelling storyline for the new season from the moment he decided to leave the comfort of McLaren for a new challenge with Mercedes.
Time will tell whether the 2008 world champion has taken a wrong turn or made the right move but, apart from careering into a tyre wall on his first day of testing, the early signs look promising.
Some remain convinced that the Briton will not be a title contender this year, and might not even win a race for his new team, but others are having second thoughts ahead of next week's season-opener in Australia.
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The man himself is sure he is on the right track and could be on to a winner.
"It's not 'no chance' and not definitely 'we will'," Hamilton said of his title prospects after he wrapped up testing with a time a second quicker than the race lap record at Barcelona's Circuit de Catalunya.
"We will definitely be able to win a race at some point," added the 28-year-old Briton, whose 21 grand prix wins have all been for McLaren - the team that backed him as a boy and gave him his F1 debut in a stunning 2007 season.
The debate over whether he was wise to turn his back on regular winners and title contenders for less competitive rivals is sure to rumble on for months to come, particularly if the new McLaren makes a strong start and the Mercedes eats tyres like it did last year.
Hamilton has said that the main target is to be competitive in 2014, when the regulations change significantly, and anything before that comes as a bonus. How much he really believes that is a moot point but the pressure will be much more on the team to deliver than on a driver whose talent is beyond doubt.