Mercedes AMG F1 had an ominous start to pre-season testing with both Nico Rosberg (pictured) and Lewis Hamilton doing barely any running on the first two days. (AFP)
Rosberg's time of 1min 20.130sec was also the best of any driver in the
four-day session and also eclipsed the fastest times set in February's first week of testing at the same Catalunya circuit.
Hamilton had clocked 1min 20.558sec in the other Mercedes on Saturday.
Former double world champion Fernando Alonso, in a Ferrari, was the only other driver to break the 1min 21sec mark on Sunday, timing 1:20.494 while 2009 champion Jenson Button was third best in the McLaren in 1:21.444.
Triple world champion Sebastian Vettel was down in eighth place in the Red Bull with a time of 1:22.514.
The new Formula One season starts in Melbourne on March 17.
Leading times:
1. Nico Rosberg (GER/Mercedes) 1:20.130
2. Fernando Alonso (ESP/Ferrari) 1:20.494
3. Jenson Button (GBR/McLaren-Mercedes) 1:21.444
4. Nico Hulkenberg (GER/Sauber-Ferrari) 1:21.541
5. Kimi Raikkonen (FIN/Lotus-Renault) 1:21.658
6. Paul di Resta (GBR/Force India-Mercedes) 1:21.664
7. Pastor Maldonado (VEN/Williams-Renault) 1:22.415
8. Sebastian Vettel (GER/Red Bull-Renault) 1:22.514
9. Valtteri Bottas (FIN/Williams-Renault) 1:22.524
10. Charles Pic (FRA/Caterham-Renault) 1:23.115
11. Jules Bianchi (FRA/Marussia-Cosworth) 1:23.167
12. Daniel Ricciardo (AUS/Toro Rosso-Ferrari) 1:23.628
13. Max Chilton (GBR/Marussia-Cosworth) 1:24.103