Sergio Perez, signed up by McLaren to replace Lewis Hamilton for the 2013 season, outshone triple world champion Sebastian Vettel to post the quickest time on the second day of testing at the Catalunya circuit in Barcelona on Wednesday.
Red Bull ace Vettel set the early benchmark with a fastest morning lap of 1 minute 22.197 seconds, but Mexican Perez, who moved to McLaren from Sauber, bettered that with a time of 1:21.848 in the afternoon.
Lotus driver Kimi Raikkonen, who failed to post a time in the morning due to a changed gearbox, took third in 1:22.697, with Hamilton steering his Mercedes into fourth.
The wraps come off the new season in Australia on March 17.
Times: 1. Sergio Perez (MEX/McLaren) 1min 21.848sec (97 laps), 2. Sebastian Vettel (GER/Red Bull) 1:22.197 (84), 3. Kimi Raikkonen (FIN/Lotus) 1:22.697 (43), 4. Lewis Hamilton (GBR/Mercedes) 1:22.726 (121), 5. Fernando Alonso (ESP/Ferrari) 1:23.247 (76), 6. Valtteri Bottas (FIN/Williams) 1:23.561 (98), 7. Daniel Ricciardo (AUS/Toro Rosso) 1:23.718 (70), 8. Paul di Resta (GBR/Force India) 1:23.971 (62), 9. Nico Hulkenberg (GER/Sauber) 1:24.205 (88), 10. Max Chilton (GBR/Marussia) 1:25.115 (66), 11. Charles Pic (FRA/Caterham) 1:26.243 (102).