Sebastian Vettel and Charles Leclerc were comfortably fastest in the first practice session for the Belgian Grand Prix as Lewis Hamilton suffered a throttle problem.
With Mercedes introducing an upgraded power unit at Spa-Francorchamps, Hamilton hit trouble on his opening run and reported a loss of power. The championship leader was rolling slowly through the middle sector but able to keep moving as it is all downhill, and eventually found a reset that gave him power back and allowed him to return to the pits.
Once back in the garage, Mercedes diagnosed an issue with the throttle pedal that required changing, meaning he missed out on a section of the early running.
The session was going much more smoothly for Ferrari, however, at a track where its straight line speed advantage should prove significant. Vettel posted a 1m44.574s to lead teammate Leclerc by a little over 0.2s, with Max Verstappen a distant third on a 1m45.507s.
Although the gap to Ferrari was big, the two Red Bulls were closely matched as Alexander Albon made an encouraging start to life at the team. Albon posted a 1m45.584s to get within 0.1s of his new teammate, although a power unit penalty will force him to start from the back of the grid on Sunday.
It was a less strong start for Pierre Gasly as he returned to Toro Rosso, finishing 18th overall and over 0.3s off Daniil Kvyat in 17th. Kvyat also had a tough session, spinning at La Source early on and reporting a spike in torque, having also taken the spec 4 Honda power unit like Albon. Similarly, Kvyat’s upgrade will lead to a back of the grid start.
Behind the Mercedes pair of Valtteri Bottas in fifth and Hamilton sixth — both on medium tires compared to softs for the rest of the field — was Lance Stroll. Racing Point and Williams have both taken the new Mercedes power unit and Stroll also has to start from the back of the grid as a result, but he started strongly with the seventh-fastest time despite causing a Virtual Safety Car when he lost a chunk of his engine cover on the run to Les Combes.
Daniel Ricciardo split the two Racing Point cars in eighth place as Renault started running its updated power unit, while Carlos Sainz — running the update in FP1 but unlikely to use it all weekend — rounded out the top 10. Both Renaults and Sainz have five-place grid penalties for their new components.
Kimi Raikkonen appeared to suffer no ill effects from a pulled muscle in his left leg as he finished 13th fastest and completed 20 laps, despite Marcus Ericsson being called up replace him if required.
The Haas pair of Romain Grosjean and Kevin Magnussen were 14th and 16th respectively, while Nicholas Latifi was nearly 0.2s clear of Robert Kubica during his latest FP1 appearance, as Williams ended up over four seconds off the pace at the back of the field.