Nico Rosberg overcame a slow start to post the fastest time in opening practice for the Belgian GP on Friday ahead of Lewis Hamilton.
Rosberg, who trails Hamilton by 21 points in the Drivers' Championship, lapped the 7.004km circuit in a time of 1:51.082s to go 0.242s faster than his Mercedes team-mate. But it was a case of making up for lost time for the German, who had earlier suffered a loss of power and was the last of the 20 runners to set a time.
In truth, it was a slow session in general, despite the sunny conditions that showed the Ardennes circuit in all its glory. Engine-saving was probably a factor for the likes of Daniel Ricciardo, who completed just 14 laps in total but still managed the third fastest time, despite Red Bull's forecast of a difficult weekend.
Next up came Ferrari, with Kimi Raikkonen fourth fastest about 0.4s faster than Sebastian Vettel. Daniil Kvyat's Red Bull was sixth, with Max Verstappen, Carlos Sainz, Sergio Perez and Valtteri Bottas completing the top 10.
In particular, the second 30 minutes of the session saw little track action. Raikkonen improved his time during this period and he was joined on track by Pastor Maldonado, although the Venezuelan then brought the session to a complete standstill after crashing his Lotus.
Maldonado's latest gaffe came at Les Combes, where he ran wide on to kerbs at the corner exit, lost control and slammed into barriers on the opposite side of the track. Two corners of the car were damaged, meaning that Lotus's mechanics face a hefty to-do list ahead of second practice.
Even so, he ended the session 11th with Lotus reserve Jolyon Palmer 17th. He in turn sandwiched the McLaren drivers - Fernando Alonso 16th and Jenson Button 18th - also suggesting a slow start for Honda's much-anticipated engine upgrades.
It's early days, of course, but amid reports of another 100bhp on tap this weekend and power output to rival Ferrari, McLaren-Honda wound up more or less where they've been all season. Furthermore, speed trap figures suggested they're still about 10km/h slower than the scarlet cars.
Second practice starts at 1pm BST.
Times:
1. N Rosberg, Mercedes, 1:51.082
2. L Hamilton, Mercedes, 1:51.324
3. D Ricciardo, Red Bull, 1:51.373
4. K Raikkonen, Ferrari, 1:51.478
5. S Vettel, Ferrari, 1:51.866
6. D Kvyat, Red Bull, 1:51.960
7. M Verstappen, Toro Rosso, 1:52.158
8. C Sainz, Toro Rosso, 1:52.421
9. S Perez, Force India, 1:52.423
10. V Bottas, Williams, 1:52.511
11. P Maldonado, Lotus, 1:52.539
12. N Hulkenberg, Force India, 1:52.614
13. F Nasr, Sauber, 1:52.640
14. F Massa, Williams, 1:52.653
15. M Ericsson, Sauber, 1:53.426
16. F Alonso, McLaren, 1:53.502
17. J Palmer, Lotus, 1:53.799
18. J Button, McLaren, 1:54.225
19. W Stevens, Manor, 1:55.501
20. R Merhi, Manor, 1:56.086