The four times world champion, 24 points behind Mercedes’ Lewis Hamilton with nine of 21 races remaining, lapped the season’s longest layout with a best time of one minute 44.358 seconds. Red Bull’s Max Verstappen, with tens of thousands of his Dutch fans expected to make the short trip across the border, was second, 0.151s slower on a largely uneventful morning with some spots of rain.
Hamilton, the 2017 winner in the Ardennes forests from pole position, ended the session third, 0.318s adrift of his German rival, with Ferrari’s Kimi Raikkonen, chasing his 100th podium this weekend and a four times winner at Spa, fourth on the timesheets.
Vettel had expressed optimism on Thursday that Hamilton could be reeled in over the remaining races, some of which should favour Ferrari more than Mercedes.
“Points-wise we know that we are a little bit behind but I don’t think it’s anything that we can’t do,” he told reporters. “I think it is has been looking for myself worse in past years and we still managed to turn it around by having the speed, so that will be the key.”
Both Vettel and Hamilton will have upgraded engines, with Mercedes saying Hamilton had a new turbocharger, engine and MGU-H and MGU-K motor generator units in his car.
Those parts were within his allocation for the season but his Finnish team-mate Valtteri Bottas incurred grid penalties after being given a completely new power unit that exceeded his allowance and will start from the bacl of the grad on Sunday, as will Renault's Nico Hulkenburg, for the same reason.
Bottas was fifth fastest in the session, ahead of Red Bull’s Daniel Ricciardo, who suffered an engine injector problem. Lando Norris made his Grand Prix weekend debut, taking Fernando Alonso’s McLaren for the session, with the 18-year-old team reserve lapping faster than under-pressure Belgian race regular Stoffel Vandoorne.
Norris, who is also chasing the Formula Two title, lapped in 1m47.364s compared to Vandoorne’s 1m47.452s. Vandoorne did only 13 laps compared to Norris’s 26, however, with the local driver kept in the garage as the team investigated a possible leak on the car.
1 Sebastian Vettel (Ferrari) 1m44.358s
2 Max Verstappen (Red Bull) +0.151s
3 Lewis Hamilton (Mercedes) +0.318
4 Kimi Raikkonen (Ferrari) +0.360
5 Valtteri Bottas (Mercedes) +0.366
6 Daniel Ricciardo (Red Bull) +1.200
7 Esteban Ocon (Renault) +1.428
8 Nico Hulkenberg (Renault) +1.593
9 Sergio Perez (Force India) +1.811
10 Carlos Sainz (Renault +1.852
11 Pierre Gasly (Toro Rosso) +1.942
12 Romain Grosjean (Haas) +2.029
13 Charles Leclerc (Sauber) +2.196s
14 Marcus Ericsson (Sauber) +2.199
15 Brendon Hartley (Toro Rosso) +2.574
16 Lance Stroll (Williams) +2.607
17 Kevin Magnussen (Haas) +2.654
18 Lando Norris (McLaren) +3.006
19 Sergey Sirotkin (Williams) +3.009
20 Stoffel Vandoorne (McLaren) +3.094