Mercedes has revealed that its evaluation work was a key factor in the varied results secured by Michael Schumacher and Nico Rosberg in qualifying at the Circuit of the Americas.

Schumacher posted the sixth best time in the session and will start from fifth on the grid thanks to Romain Grosjean's five-place grid penalty, but Rosberg could only trail in 17th - leaving him with work to do on race day.

Schumacher's performance came after a difficult run of form for the seven-time champion and he said he was pleased with the result ahead of his penultimate race before retirement.

The German was however lucky to escape punishment for an incident that saw him delay Fernando Alonso's Ferrari during the second stage of the session, with stewards electing not to penalise the Mercedes man as neither driver was on a flying lap.

"Qualifying was better than we expected, especially as we have struggled over the weekend and have worked hard to make progress and achieve such a solid job today," he said. "Qualifying in sixth place is a good and important position for us as a team. I had a good lap in Q3 and everything felt right with the car so we were able to maximise the potential.

"It will make a big difference here whether you start from the clean or dirty side of the grid, so gaining an extra place due to Grosjean's penalty was a nice surprise. The car looks reasonably consistent for the race and I would like to achieve the maximum result possible tomorrow."

While Schumacher continued to run with Mercedes' coanda exhaust, Rosberg ran with a standard part as the team evaluates data for 2013 and he struggled to get the tyres on his car to work in the session.

"I ran our old exhaust system in qualifying today as part of our evaluation programme for next year," he said. "We had already used it yesterday and made the decision to continue for the rest of the weekend to help with the learning process. The car felt good this morning in the cool temperatures but the difference to Michael's car surprised me this afternoon. So I hope that the race pace is better tomorrow and the switch will be worth it. I will definitely push to score points."