Button on top for McLaren in final practice

Jenson Button kept McLaren on top of the time-sheets when he clocked the fastest lap in Saturday morning's third and final free practice session ahead of this weekend's title showdown Brazilian Grand Prix. The 32-year-old Briton took over from team-mate and compatriot Lewis Hamilton, who had topped the times in both sessions on Friday as hot and humid weather replaced the blue skies and McLaren continued to upstage the championship protagonists. Defending champion Germany's Sebastian Vettel, who needs to finish fourth or better to be certain of becoming the youngest triple champion in Formula One hitory, was second fastest ahead of his Red Bull team-mate Australian Mark Webber. Button's McLaren team-mate Hamilton was fourth fastest in a closely-fought session that saw the top four drivers separated by only two-tenths of a second. Vettel's only remaining title rival, two-time champion Spaniard Fernando Alonso of Ferrari, was eighth-fastest for Ferrari and his team-mate and local hero Brazilian Felipe Massa was down in 10th. Button clocked his fastest lap of one minute and 13.188 seconds in the closing seconds of the session after earlier topping the times with a quick lap in the 18th minute of the hour's high-temp action. Frenchman Romain Grosjean of Lotus was fifth ahead of Briton Paul Di Resta and his Force India team-mate German Nico Hulkenberg. Venezuelan Pastor Maldonado was ninth for Williams. The session was run in sultry heat with a track temperature of 36 degrees Celsius and an air tepmperature of 28 degrees. Finn Kimi Raikkonen, winner of the Abu Dhabi Grand Prix this year, was forced to retire from the fray after only 14 minutes when the Renault engine in his Lotus car failed.