It was business as usual for Mercedes in Montreal on Friday afternoon as Lewis Hamilton topped the timesheets ahead of Nico Rosberg.
Valtteri Bottas held down the P1 slot at the start of the session. His 1:17.597 was 0.013s up on Rosberg while Hamilton was a further 0.015s down.
The trio then changed positions with Rosberg hitting the front while Hamilton improved to second. They were separated by 0.173s while Bottas was overhauled by Fernando Alonso for third.
Rosberg, having asked what "did my team-mate do", found some extra speed on the soft Pirellis and lowered the benchmark to a 1:16.777.
His reign, though, came under threat from Hamilton who clocked a 1:16.692 to lead the timesheets.
Swapping to the supersoft tyres 40 minutes in, Rosberg edged Hamilton by 0.005s only for the Brit to come through with a 1:16.118, half a second up on his team-mate.
Rosberg closed the gap to 0.175s while Kimi Raikkonen went third, 0.530s down. Alonso was a further 0.053s off the pace.
The Ferrari pairing, though, were edged by Sebastian Vettel as the Red Bull racer came through in third place with a late supersoft run.
Felipe Massa was sixth ahead of Valtteri Bottas and the McLaren drivers of Kevin Magnussen and Jenson Button.
There were issues in the session for Pastor Maldonado who was given a free trip in the pitlane when his E22 broke down when he tried to practice a start. This led to his mechanics pushing him down the pitlane but he was soon back in the action.
The same cannot be said of Marcus Ericsson who made a mistake that ended with him down an escape road. With no place to throw a U-turn his session was over.
Another backmarker, Jules Bianchi, managed just three laps because of what sounds like an engine related issue while car troubles meant Daniil Kvyat was limited to nine laps.
01 Lewis Hamilton Mercedes 1:16.118 42 laps
02 Nico Rosberg Mercedes 1:16.293 +0.175 39 laps
03 Sebastian Vettel Red Bull 1:16.573 +0.455 26 laps
04 Kimi Raikkonen Ferrari 1:16.648 +0.530 31 laps
05 Fernando Alonso Ferrari 1:16.701 +0.583 27 laps
06 Felipe Massa Williams 1:16.774 +0.656 37 laps
07 Valtteri Bottas Williams 1:16.893 +0.775 37 laps
08 Kevin Magnussen McLaren 1:17.052 +0.934 42 laps
09 Jenson Button McLaren 1:17.059 +0.941 38 laps
10 Jean-Eric Vergne Toro Rosso 1:17.180 +1.062 40 laps
11 Romain Grosjean Lotus 1:17.626 +1.508 28 laps
12 Daniel Ricciardo Red Bull 1:17.644 +1.526 36 laps
13 Nico Hulkenberg Force India 1:17.712 +1.594 35 laps
14 Sergio Perez Force India 1:17.819 +1.701 33 laps
15 Pastor Maldonado Lotus 1:17.868 +1.750 27 laps
16 Adrian Sutil Sauber 1:17.964 +1.846 47 laps
17 Esteban Gutierrez Sauber 1:18.340 +2.222 43 laps
18 Max Chilton Marussia 1:18.693 +2.575 34 laps
19 Daniil Kvyat Toro Rosso 1:18.732 +2.614 9 laps
20 Kamui Kobayashi Caterham 1:20.244 +4.126 38 laps
21 Marcus Ericsson Caterham 1:22.418 +6.300 13 laps
22 Jules Bianchi Marussia 1:32.127 +16.009 3 laps