Vettel hits back in final practice
The 24-year-old German, winner in Brazil last year and chasing a record 15th pole position of the season later in the afternoon, was 0.087 seconds quicker than McLaren's Jenson Button with a best lap of one minute 12.460 seconds.
Vettel and Red Bull have already won both this year's championships.
Australian Mark Webber, Vettel's team mate who has yet to win a race this season despite setting more fastest laps than anyone else in the 18 races so far, was third fastest at one of his favourite circuits.
Conditions were hot, with a track temperature of around 42 degrees, but rain has been widely forecast for Sunday which could make the race more of a lottery.
Ferrari's Felipe Massa, twice a winner of his home race and preparing for his 100th start for the Italian team, was 10th only and had a near-miss with Michael Schumacher's Mercedes in the closing minutes.
"We know it's a hydraulics leak. We will try to fix it quickly but it's going to be difficult as we still don't know where the leak is. If we take off the floor to have a look, it'll take at least 15 minutes to get it back on," said the Swiss.