By Ian Ransom
MELBOURNE (Reuters) - Mercedes driver Nico Rosberg topped the timesheets in final practice at the Australian Grand Prix on Saturday as rain, gusty winds and reliability problems dominated an eventful session.
The German lapped the Albert Park circuit in one minute 29.375 seconds, well ahead of McClaren's Jenson Button by 1.391 seconds on a warm day in Melbourne.
With teams still grappling with the new turbopowered hybrid engines, a light downpour 10 minutes into the session added another layer of complexity, and a number of drivers careened off the bumpy street circuit and ploughed through gravel and grass.
Two-time world champion Fernando Alonso was third fastest, with Lewis Hamilton, who topped the second free practice on Friday, fourth in his Mercedes.
Kimi Raikkonen, the 2007 world champion, was held up in the garage with a radio problem for much of the session, but emerged to post the seventh fastest lap for Ferrari.
It was a difficult session for reigning quadruple champion Sebastian Vettel, who oversteered, skidded over the grass and complained of acceleration problems as he pushed for a faster time on the soft tires late in the session.
"Horrible. The car doesn't accelerate," the Red Bull driver barked over the team radio.
After being unable to post a lap time in either of Friday's sessions due to reliability problems, Lotus driver Pastor Maldonado finally managed to get on the timesheets after being told to be wary of a brake problem.
He was 18th out of 19 drivers who recorded times, however.
His team mate Romain Grosjean was not so fortunate, and headed back to pit lane, exclaiming "unbelievable!" on his team radio after experiencing engine problems on his installation lap.
Sauber driver Esteban Gutierrez was also unable to post a lap time, and rolled slowly back to pit after experiencing a gear-box problem.
The Williams team's relatively trouble-free start to the season came to an end as Finnish driver Valtteri Bottas was unable to leave the garage.
Japan's Kamui Kobayashi finally consummated his F1 return with a run for Caterham, finishing 16th fastest.
(Editing by Sudipto Ganguly)