Mark Webber was fastest Thursday at the last Formula One testing session before the start of the new season gets under way.
The Red Bull driver set a best lap time of 1 minute, 21.487 seconds around the Circuit de Catalunya - nearly a second faster than Nico Hulkenberg of Williams.
Nico Rosberg of Mercedes GP, Sauber's Pedro De la Rosa and Jenson Button of McLaren were the only other drivers within two seconds of the Australian.
Tonio Liuzzi of Force India was sixth, while Fernando Alonso of Ferrari was seventh as the Spaniard was hampered by a mechanical problem.
Webber also had a problem that required his car's removal from the track, with Red Bull mechanics cloaking the vehicle to keep it covered from onlookers before it was returned to the garages.
Red Bull is among the leading teams expected to fight for the championship this season. The group also includes McLaren, Mercedes and current favorite - based on testing form - Ferrari, where Alonso is going for his third championship.
"Clearly we have the pace. I hope that we will be strong," Webber said ahead of the season-opening Bahrain Grand Prix. "But you're Spanish friend won't be far behind."
Rosberg expects a big jump in performance from the former Brawn GP team by the March 14 opener, but the contenders remain too tough to name.
"It's difficult to say, I think it's close at the moment," the German driver said. "It's such a big step we're bringing to Bahrain it could change things again. So it's not ideal to make any suggestions at the moment."
Virgin Racing's problematic start continued as rookie driver Lucas di Grassi spun out at corner nine and ran into the tire wall to end the team's running. The British team had to fly in replacement parts overnight to fix the damage to the rear of the car and is trying to repair a hydraulics problem.
"Next time I will go even faster, always pushing more and more," Di Grassi wrote on his Twitter page.
Lotus continued its testing program, with reserve driver Fairuz Fauzy coming last among the 11 cars - more than six seconds off the pace set by Red Bull.
But the Malaysian driver said the most important thing is to avoid making mistakes.
"We're still far off but there is still improvement to be had," said Fauzy, who is hopeful of closing to three seconds of the pace setters by the start of the season. "We need to be realistic."
Fellow rookie teams Campos Meta and USF1 are not in Barcelona, with the latter reportedly on the verge of folding.
The American team is hoping to find sponsorship and funds as it lobbies governing body FIA to allow it to miss the first couple of races because it will not be ready in time.
Campos expects to be ready to race at Bahrain.