The GermanÃ¢â‚¬â„¢s one minute 38:052 was one tenth quicker than RenaultÃ¢â‚¬â„¢s Robert Kubica who had set his own stunning lap just minutes before.
Just one second covered the top 12 drivers ahead of qualifying later this afternoon, with the top six separated by just half a second and no team really dominating.
McLaren had problems on both cars, Lewis Hamilton a minor issue with the front left brake, while Jenson Button needed a gurney flap added to his rear wing to counter instability through the fast corners.
As McLaren struggled, both Force India and Williams took advantage with Adrian Sutil looking competitive throughout final practice to take fourth quickest with a time of 1:38:500, while Barrichello took sixth for Williams with a 1:38:623, and SutilÃ¢â‚¬â„¢s team mate Tonio Liuzzi took seventh with a 1:38:676.
Virgin RacingÃ¢â‚¬â„¢s Lucas Di Grassi set the first lap of one minute 43:867 almost twenty minutes into final practice as many cars waited for the smaller teams to go out and start the process of bedding in the track.
Fernando Alonso was quick from his first run, setting the fastest lap before Vettel, Kubica, Mark Webber and Force IndiaÃ¢â‚¬â„¢s Adrian Sutil, all jumped ahead as teams switched to the option tyres for the final runs, as Alonso settled for third fifth fastest with a 1:38:513.
After a steady pace throughout practice the action picked up in the last five minutes with all cars on track as the teams made their final preparations for qualifying.
At the back, Lotus were again the quickest of the new teams as Heikki Kovalainen finished 1.5 seconds off the slowest of Sauber of Pedro De La RosaÃ¢â‚¬â„¢s 1:39:699.
Michael SchumacherÃ¢â‚¬â„¢s poor form continued as the seven-time world champion could only manage fifteenth quickest with a 1:39:222, behind rookies Nico HÃƒÂ¼lkenburg and Vitaly Petrov. SchumacherÃ¢â‚¬â„¢s team mate Nico Rosberg recorded the eleventh quickest time behind the McLarens with a 1:38:822.
Ferrari, Red Bull and Renault look strong for qualifying following final practice, with McLaren and Mercedes set for a battle to join the top six.
But are McLaren sandbagging? It would be an unusual move, but it is clear that Ferrari and Red Bull are making good use of the F-duct and blown diffuser combination Ã¢â‚¬â€œ McLaren have just the F-duct, while Renault have just the blown diffuser.
Qualifying is at 13:00 BST Live on BBC 1/Red Button/BBC website in the UK.
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