Red Bull’s Max Verstappen headed Ferrari’s Kimi Raikkonen in second practice at the Canadian Grand Prix.
Verstappen’s team-mate Daniel Ricciardo leapt up to third place late on after electrical problems delayed him.
But Lewis Hamilton’s Mercedes appeared to be quickest, fourth and 0.579 seconds off the pace on a slower tyre.
The session was characterised by teams juggling tyres to work out their best strategy for qualifying and race with the awkward hyper-soft rubber.
The hyper-soft is much faster over one lap than the ultra-soft, the medium of three compounds this weekend, but it degrades much faster than other two, and at least some of the top three teams are likely to try to avoid starting the race on it.
All three potentially have the pace to make it through the second qualifying elimination session on the ultra-soft, which would mean they could start the race on that tyre and avoid the hyper-soft, using it only for the top 10 shoot-out at the end of qualifying.
But that will not be known for sure until qualifying on Saturday.
So who looks fastest for the race?
The mix of tyres made it difficult to get an accurate read on overall pace but Hamilton, who is always stunning around the demanding Circuit Gilles Villeneuve on the picturesque Ile Notre-Dame in the St Lawrence Seaway, looked imperious.
His lap time of one minute 12.777 seconds was 0.579secs off Verstappen’s fastest but set on the hardest and slowest tyre, the super-soft, which is reckoned to be at least a second slower than the hyper-soft used by Red Bull and Ferrari.
Mercedes did not run the hyper-soft tyre at all on Friday, preferring to save it for Saturday because they have chosen to bring only five sets for each driver – the fewest of any team.
By contrast, Verstappen – who was also fastest in first practice – Raikkonen, Ricciardo and Vettel all used the hyper-soft to set their times, the Dutchman 0.13secs ahead of the Finn and 0.405secs clear of the Australian.
But Ricciardo’s session was hampered by an electrical problem which cost him the best part of an hour of track time, and when he did get back on track he had to negotiate the rest of the cars doing race-simulations runs on full tanks up to six seconds a lap slower than him.
Vettel’s day was also difficult. He missed the start of the session as the Ferrari mechanics worked on an issue the team have not revealed and appeared to lack pace when he was running. The German was 0.787secs off Verstappen while also running the hyper-soft tyres.
Best of the rest was Haas driver Romain Grosjean, who pipped the Force Indias of Esteban Ocon and Sergio Perez, all three running the hyper-soft tyre.
McLaren’s Fernando Alonso was only 0.246secs behind Grosjean in 10th place, despite only running the ultra-soft, capping a strong day for the team, who have new aerodynamic parts, including a new front wing, in addition to an upgrade enjoyed by all Renault-engined cars.
The factory Ferraris and Toro Rosso-Hondas also have engine upgrades this weekend. Mercedes are not using theirs after discovering a “quality issue” that would have risked the engine’s reliability over the seven races it has to complete.
What they said
Hamilton: “Beautiful day, weather is fantastic and the track feels amazing. It feels great. We enjoyed it. Didn’t have any problems, such a fun track to drive.
“We don’t have as many hyper-softs as everyone else. You have to select them quite far ahead. Hindsight is a great thing. It would have been great to try the hyper today but others have and seen some that degraded a lot and some maybe haven’t but in P3 we will take it for a spin and have a look at it.”
Vettel: “Not entirely happy yet. For us it is not quite there. We still have some work to do.”