Sao Paulo: Nico Rosberg splashed through spray and standing water to put Mercedes on top in both practice sessions for the season-ending Brazilian Grand Prix at a rainswept Interlagos on Friday.
The German was quickest in the morning with a best time of one minute 24.781 seconds, set early on before track conditions became more treacherous, and saw off the Red Bulls in the afternoon with a lap of 1:27.306.
Team mate Lewis Hamilton had been second quickest before lunch but Red Bull`s quadruple world champion Sebastian Vettel and Mark Webber completed the top three in the second session.
Webber, preparing for his final Formula One race with both world titles already won by his team and Vettel, suffered another of the KERS failures that have plagued his recent career.
Finland`s Heikki Kovalainen, filling in at Lotus for compatriot Kimi Raikkonen, was fourth fastest in the afternoon ahead of Hamilton.
The times were largely meaningless with the weather triggering plenty of slides, spins and off-track excursions as cars aquaplaned and drivers were unable to do any long-run preparation.
More rain is expected on Saturday for final practice and qualifying.
Vettel was alone in trying out Pirelli`s slick 2014 development tyre in the morning, completing a cautious lap with sensors on the car before being told by his race engineer that they had all the data they needed.
The German can equal compatriot Michael Schumacher`s 2004 record of 13 wins in a season as well as Italian Alberto Ascari`s 60-year-old record of nine victories in a row if he triumphs on Sunday.
Vettel already holds the record for eight successive wins in a single season.
BATTLE FOR SECOND
With the championships wrapped up last month, the main focus for his rivals this weekend is the battle for second place between Mercedes, Ferrari and Lotus as well as various farewells.
Mercedes are 15 points ahead of Ferrari with Lotus a further 18 behind.
McLaren`s Jenson Button - last year`s winner at the Sao Paulo circuit - was fourth quickest in the morning but last in the second practice ahead of a weekend that could see his team`s season confirmed as their worst in decades.
If 2009 world champion Button or Mexican Sergio Perez fail to finish in the top three on Sunday, it will be the first time since 1980 that McLaren have gone a whole season without a podium appearance.
Ferrari`s Fernando Alonso was fifth and 11th, while Brazilian team mate Felipe Massa was 11th and seventh for his last race in the Italian team`s colours before moving to Williams.
Russian teenager Daniil Kvyat stood in for Australian Daniel Ricciardo, the man he is replacing full time next year, at Toro Rosso for the first session and was an impressive eighth in his second involvement in a grand prix weekend and first in wet conditions.
Paul Di Resta also sat out the morning at Force India, with British reserve James Calado in his car.