Sergio Perez of Sauber set the pace in the second-to-last day of testing before the new Formula One season gets under way.
The Mexican driver steered his way to a fastest lap of 1 minute, 22.094 seconds at the Catalunya Circuit before rain showers slowed down the afternoon session.
McLaren's Jenson Button came in just 0.009 seconds behind. Daniel Ricciardo of Toro Rosso was third, in front of Ferrari's Felipe Massa in fourth.
Mark Webber tried out Red Bull's latest modification to this season's car and finished with the eighth fastest time.
Trouble with the steering left Kimi Raikkonen of Lotus as the slowest of the 10 drivers.
The season opens at the Australian Grand Prix on March 18.