MEXICO CITY • Formula One championship leader Nico Rosberg wound up third in Friday's second free practice at the Mexican Grand Prix and said he faced "a lot of homework to do" to improve his performance for the weekend's main race.

The German was four-tenths of a second off the pace set by fastest man Sebastian Vettel of Ferrari and his Mercedes team-mate, defending champion Lewis Hamilton.

"It's been an unusual day out there," said Rosberg, who is 26 points clear of Hamilton with three races remaining. "We have low temperatures and a very green track.

"So, it's been a bit of a steep learning curve to understand what to do with the tyres - how to get the best out of them and also the long runs.

"We really learnt a lot and it's not been a bad start overall, but we have a lot of homework to do.

"The car was feeling okay on the medium tyres, but even there, we need to make some progress to understand where we can find some more performance."

Hamilton, on the other hand, said he was enthused by the big and enthusiastic Mexican crowds and he had a solid day in terms of race preparation.

"The cars are faster, but our lap times are pretty strong already," the Briton said.

"The track feels better to me than it did last year and I feel a lot more comfortable in the car so I hope I can carry that right through the weekend."

Hamilton was fastest ahead of Vettel in Friday morning's opening practice session and knows he has to repeat his victory in last Sunday's United States Grand Prix to keep his title challenge alive.

Vettel ousted Hamilton from the top in the afternoon, by just 0.004sec, with a lap of 1min 19.790sec on super-soft tyres that showed Ferrari are not about to let Sunday's race turn into another Mercedes duel.

It was the first time the Italian team had led a Formula One practice session since Belgium in August.

REUTERS, AGENCE FRANCE-PRESSE

F1 MEXICAN GRAND PRIX

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