Sebastian Vettel refused to get too carried away despite topping the times on the opening day of the second pre-season F1 test at Catalunya.

The Red Bull driver posted the best time of 1min 23.265secs during the afternoon session to emerge top of the pile, although the defending champion was also quicker than Force India's Nico Hulkenberg with his second best time of the day.

It proved to be a trouble free day of running for the new RB8 in its second test on track but Vettel said it was hard to tell exactly where the team stands given the different programmes being employed by teams in the paddock.

"It's clear that the cars have less grip than last year, but we try to come back from that slowly," he said. "It's difficult to judge where we are compared with the others right now. It's all based on feeling and the feeling I have inside the car at the moment is fine. I think we had a good day today, with no trouble. We had a long lunch break when we made some changes, but not because anything broke down. All in all, it was a good day."

Head of Race Engineering Ian Morgan said that the changes over lunch had been the reason for some lost track time, although it didn't hinder the team too much in its planned programme.

"We got through most of what we wanted today," he said. "We had a longer than usual break for lunch, in order to change some things, but that had always been planned. So, while we lost a little time, it wasn't at the expense of getting the tasks completed.

"These tests are a process of continuous development and the programme today was influenced a bit by what we learned at the last test. We also had to test some items that were put into development before the car even took to the track. The next two days will be somewhat different.

"We will be doing race simulations and will have the whole race team here, so we will try to mix that with continuing the development. There aren't many chances to run through a whole race weekend before the season starts and we'll do a simulation with each driver. Those should keep us on our toes for the next couple of days."