Lewis Hamilton was in scintillating form as he set the pace in second practice at the Canadian Grand Prix.
The world champion headed Ferrari's Sebastian Vettel by 0.257 seconds and was more than half a second clear of Mercedes team-mate Nico Rosberg.
Red Bull's Max Verstappen and Daniel Ricciardo were next, both 0.9secs off Hamilton, separated by only 0.012secs.
Jenson Button was an encouraging seventh for McLaren, matching the time of Williams' Valtteri Bottas in sixth.
Button's team-mate Fernando Alonso was 0.197secs behind in 11th place, setting his fastest lap earlier in the session. The McLaren drivers were separated by Ferrari's Kimi Raikkonen, Force India's Nico Hulkenberg and Toro Rosso's Carlos Sainz.
Hamilton is currently 24 points off Rosberg in the championship, ahead of a weekend when the circuit will, as ever in Montreal, be packed with about 100,000 enthusiastic fans.
Changeable weather is predicted for Sunday's race, which will be live on the BBC Sport website and radio 5 live Sports Extra.
Hamilton took his first victory of the year in Monaco last time out, closing the margin between the two Mercedes drivers by 19 points as Rosberg struggled to seventh.
And the Briton has looked like a man on a mission since he took to the Circuit Gilles Villeneuve in first practice on Friday morning.
He set the pace in the first session, 0.331secs quicker than his team-mate, and was nearly 0.9secs than the German on the first runs in second practice.
Hamilton was then quicker on his first lap as they did their qualifying simulations on the ultra-soft tyres than Rosberg managed on his second, which was marginally faster than his first.
The world champion also had an advantage of about 0.2secs on average on the race-simulation runs later in the session, when the cars are filled up with fuel and the drivers try them as they will be set up at the start of the grand prix.
The gaps suggest that Mercedes, at least in Hamilton's hands, still have a comfortable margin over the rest of the field after Red Bull set the pace in Monaco.
"It's been an awesome day," said Hamilton. "This has always been a strong circuit for me and I'm really enjoying being back here again. I've generally been really happy with the car so far."
Rosberg said: "Generally I feel good in the car. But getting the tyres working is not so straightforward here, so that needs some further analysis tonight."
And at least on Friday Red Bull do not appear to have emerged as the second fastest team despite the 0.5-second-per-lap improvement in the upgraded Renault engine both drivers are using this weekend.
"I've always enjoyed driving around here," said Ricciardo. "Bouncing over the kerbs, it's a lot of fun. I don't think we quite got everything out of it today but I think if we put it all together we can be pretty close with Ferrari. With the right lap, we can be ahead of them."
Behind the Mercedes and Vettel, the field is very closely packed - just over half a second separated Bottas in sixth from Toro Rosso's Daniil Kvyat in 14th.
"The car is always very alive here," said Vettel. "It is a rough ride. All the new bits we brought are giving us what we expected so that is good news for today."
Ferrari have a new turbo design, plus some new Canada-specific bodywork.