Lewis Hamilton could again prove to be a fly in the ointment ahead of this weekend's title showdown in the Brazilian Grand Prix.

Although no longer involved in the championship battle, Hamilton has designs on finishing his 14-year association with McLaren with back-to-back victories after completing his final Friday practice with the team by setting the fastest times in both sessions.

In Sunday's United States Grand Prix, Hamilton proved a thorn in the side of Sebastian Vettel by denying the 25-year-old a win that would have seen him take a 20-point lead over title rival Fernando Alonso.

Instead, Vettel's cushion is only 13 points going into the eagerly-anticipated race at Interlagos - as one of the two will become a three-time Formula One world champion.

It paves the way for further scenarios to come into play, especially if Hamilton goes out on a high with his maiden Brazilian triumph.

The 27-year-old, who has decided to join Mercedes next season on a three-year contract, topped the timesheet with a lap around the undulating 4.309km track of one minute 14.026secs.

Vettel, who had finished second to Hamilton in FP1 by just 0.009secs, was a little further adrift in FP2, falling 0.274secs behind in his Red Bull.

Team-mate Mark Webber found himself half a second off the pace, and had the Ferraris of Felipe Massa and Alonso in close attendance as they finished 0.527secs and 0.556secs adrift respectively.

With a track temperature nudging 50 degrees, one of the hottest of the year, and with an air temperature of 33 degrees, such times and running could all be for nothing.

Heavy rain continues to be forecast for Sunday, with the only real question as to when it will hit Sao Paulo - before, during or after the race.

Alonso certainly requires any variable to assist his cause if he is to nick the championship from Vettel.

Behind the leading quintet, on his 308th and final grand prix before retiring for a second time, seven-times champion Michael Schumacher at least suggested he could bow out on a respectable note.

In his Mercedes, the 43-year-old and team-mate Nico Rosberg were sixth and seventh quickest, just over six tenths of a second down.

They were followed by Jenson Button in his McLaren and Lotus' Romain Grosjean, the only other drivers within a second of Hamilton.

Paul di Resta again showed good pace in his Force India to complete the top 10, and was back on a par with team-mate Nico Hulkenberg, the duo a second adrift and separated by just two thousandths of a second.

Kimi Raikkonen, who yesterday missed his media duties after missing a flight from Los Angeles, was down in 12th in his Lotus and struggling as he complained of lack of grip with his tyres.

At the bottom of the timesheet, where he has been almost all season long, was India's Narain Karthikeyan in his HRT, a team that could be competing in their last race this weekend due to financial woes.

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