Rosberg: Early tests of 2016 parts right thing to do

The German and teammate Lewis Hamilton devoted their Friday morning running at Interlagos to evaluating new ideas for next year's Mercedes challenger – including a S-duct vent concept – before the parts were removed for the second session.

And although the programme could compromise their race preparations, Rosberg thinks it wholly right that Mercedes trials new developments.

"Why are we testing new things? Because both championships are over," said Rosberg. "The team won the constructors' championship and Lewis the drivers' championship, so there's nothing else to do this year.

"For me the position is not that important. More important it is to learn for next year and do tests. So we are testing many things."

When asked how successful the morning's tests had been, Rosberg said: "Did the new parts work? I don't know for the moment. It's very early and we must see."

Hamilton was less forthcoming about the development tests on Friday.

"I don't know what it is. I didn't know we had a new nose. I don't know what the S-duct is."

Tight battle

With the Mercedes drivers topping the times in both sessions, Hamilton said he was predicting a tight battle.

He also played down talk his pace had been helped by him running a wrong engine mode.

"We always have different engines modes," he said. "We didn't have the exact same one, but he did a very good lap in FP2, but I think it's going to be close.

"Last year in the race. I had a really good pace and I guess this weekend I really need to push for that qualifying position because that determines really the race."

Additional reporting by Federico Faturos