France's Romain Grosjean, in a Lotus, set the fastest time in Formula One testing on Friday, making the most of dry afternoon conditions, in marked contrast to the wet surface of the morning session.
Grosjean's time of 1min 22.716sec was half a second faster than McLaren driver Jenson Button's best of the morning at the Catalunya Circuit.
Button, the 2009 world champion, had clocked 1min 25.936sec before improving to 1min 23.181sec in the afternoon.
"Even though the weather was far from ideal it was a pretty good day for us and it's certainly a better feeling to end the session with the fastest time on the board rather than the slowest," said Grosjean, who will hand testing duties to Kimi Raikkonen for the final two days.
"I wish I could have more time in the car before the season starts, but if we're in the same position on the monitors when we get to Australia I'll be very happy indeed."
World champion Sebastian Vettel was fourth quickest in the Red Bull, a day after teammate Mark Webber had been the fastest man on the track.
"I didn't do that many laps today, but to be honest the weather wasn't great and it was a pretty rough day in terms of the wind," said the German, who drove 63 laps.
"It's very cold as well. The tyres aren't really working properly and I think everybody is suffering the same problem, struggling to make the tyres last for more than a lap."
Australian Daniel Ricciardo was an encouraging seventh in his Toro Rosso-Ferrari.
The four-day testing session ends on Sunday ahead of the start of the 2013 season in Melbourne on March 17.
1. Romain Grosjean (FRA/Lotus-Renault) 1min 22.716sec (85 laps), 2. Jenson Button (GBR/McLaren-Mercedes) 1:23.181 (70), 3. Pastor Maldonado (VEN/Williams-Renault) 1:23.628 (72), 4. Sebastian Vettel (GER/Red Bull-Renault) 1:23.743 (63), 5. Nico Hulkenberg (GER/Sauber-Ferrari) 1:23.744 (77), 6. Adrian Sutil (GER/Force India-Mercedes) 1:24.215 (62), 7. Daniel Ricciardo (AUS/Toro Rosso-Ferrari) 1:25.483 (59), 8. Max Chilton (GBR/Marussia-Cosworth) 1:25.598 (73), 9. Giedo van der Garde (NED/Caterham-Renault) 1:26.316 (48), 10. Nico Rosberg (GER/Mercedes) 1:26.655 (117), 11. Fernando Alonso (ESP/Ferrari) 1:27.878 (100)