Robert Kubica said he was not getting too excited about his positions in Friday practice at Interlagos, as he felt his Renault was not quite up to speed yet. The Pole was in the top six in both sessions, but played down the results.
"Our position looked pretty good in both sessions today but we know from experience that Friday can be misleading, so we need to be cautious," said Kubica. "The main target overnight will be to improve the balance of the car because it was not ideal today - I was struggling with inconsistency and low grip.
"None of the changes we made really allowed us to make a big step forward, so we need to work hard this evening to make progress."
Renault's chief race engineer Alan Permane acknowledged that the team had work to do for Kubica.
"It was actually a bit of a frustrating day, and we struggled to find a car balance that Robert was happy with," said Permane. "He suffered from inconsistency, probably owing to the low-grip surface here, and we will work tonight to improve that and make the car easier to drive."
Kubica's teammate Vitaly Petrov crashed in the morning session, with the team putting the incident down to a rear wing problem. The Russian was 15th in both sessions.
"Vitaly endured a very tricky day," Permane said. "A problem with the rear wing caused him to crash during this morning's session, and the mechanics did a good job to get him out in good time in the second session. But he was always playing catch-up after that, and never really got comfortable with the car balance."