Mark Webber of Red Bull drove the fastest lap on Tuesday on the opening day of the final Formula One testing session before the start of the new season.
The Australian's time of 1 minute, 22.544 seconds at Catalunya Circuit was also faster than any lap from the session here last month.
"It was a pretty good day and not much has changed since last week," Webber said. "I think everybody is limited by tires - we don't have unlimited sets of tires these days, so the mileage is a bit controlled by how many you have at your disposal."
Jenson Button's lap of 1:22.910 in his McLaren was next quickest as the British team tried out a new front wing.
"The last couple of tests haven't been perfect for us, and I think that's partly due to us lacking setup work," the 2009 world champion said. "There's not much testing left - I only have one more day in the car - but, after today, I feel we can make further positive progress over the next few days."
Mexican driver Sergio Perez of Sauber finished between Renault pair Vitaly Petrov and Nick Heidfeld to round out the top five as eight of the 11 teams tested, with most bringing new aerodynamic packages to their cars.
Luiz Razia of Team Lotus was 10th with a lap of 1:26.723, while Jerome d'Ambrosio was nearly 10 seconds off Webber's pace to finish last in his Virgin Racing car.
The session, which runs until Saturday, was originally supposed to be held in Bahrain ahead of the season-opening grand prix. But anti-government unrest forced organizers to postpone the race. Organizers have until May 1 to propose a new date for the race.
The Australian GP will now open the season on March 27.