While most of his rivals made inroads on the supersoft tyres, Lewis Hamilton's 1:15.610 on the softs was good enough to hand him another P1 in Montreal.
Kevin Magnussen laid down the first benchmark in his MP4-29, crossing the line with a 1:20.9 on a warm and dry Circuit Gilles Villeneuve. He lowered that to a 1:18.3 and led the way until 25 minutes in when Sergio Perez crossed the line with a 1:18.1.
The Force India driver's time at the front was very short-lived as moments later Hamilton went quickest only to be overhauled by Kimi Raikkonen and then Fernando Alonso.
Hamilton came back with a 1:16.760, taking half a second out of Alonso's lap time. He extended his advantage with a 1:16.186 while the Williams drivers improved to second and third with Felipe Massa, quickest in the speed trap, ahead of Valtteri Bottas.
However, it was all change as Nico Rosberg came through with a 1:16.128. That sparked the expected Mercedes tussle as he then went even quicker before his team-mate responded with a 1:15.610.
Swapping to the quicker supersoft tyres for the final 20 minutes, the Ferrari drivers were the first to make the move but Alonso's time put him 0.8s behind the Mercs while Raikkonen was 0.9s adrift. And the Mercedes drivers had yet to do their supersoft runs.
However, when they did venture out neither Hamilton nor Rosberg were able to make any inroads on their previous bests allowing Massa to split them with a 1:16.086.
Alonso finished in fourth place ahead of Daniel Ricciardo, Raikkonen and Bottas. Daniil Kvyat completed the top eight.
There were moments for Magnussen at Turn 8 and Marcus Ericsson and Sergio Perez at Turn 8 while Esteban Gutierrez's practice came to an end just 15 minutes into the session when he crashed at Turn 4.
The Sauber driver lost it on entry to Turn 4, put his Sauber into a slide and hit the wall. The C33's rear left took the brunt of the impact although the front left wasn't unscathed.
The red flags were waved with the marshals quickly on hand to clear the debris and the session resumed three minutes later.
Kamui Kobayashi also failed to reach the chequered flag as his Caterham broke down with six minutes remaining.
01 Lewis Hamilton Mercedes 1:15.610 18 laps
02 Felipe Massa Williams 1:16.086 +0.476 16 laps
03 Nico Rosberg Mercedes 1:16.120 +0.510 20 laps
04 Fernando Alonso Ferrari 1:16.488 +0.878 15 laps
05 Daniel Ricciardo Red Bull 1:16.504 +0.894 15 laps
06 Kimi Raikkonen Ferrari 1:16.528 +0.918 22 laps
07 Valtteri Bottas Williams 1:16.684 +1.074 20 laps
08 Daniil Kvyat Toro Rosso 1:16.820 +1.210 21 laps
09 Jean-Eric Vergne Toro Rosso 1:16.824 +1.214 19 laps
10 Sebastian Vettel Red Bull 1:16.884 +1.274 15 laps
11 Nico Hulkenberg Force India 1:16.944 +1.334 17 laps
12 Kevin Magnussen McLaren 1:16.993 +1.383 19 laps
13 Romain Grosjean Lotus 1:17.121 +1.511 21 laps
14 Sergio Perez Force India 1:17.188 +1.578 19 laps
15 Pastor Maldonado Lotus 1:17.224 +1.614 20 laps
16 Jenson Button McLaren 1:17.360 +1.750 23 laps
17 Adrian Sutil Sauber 1:17.900 +2.290 23 laps
18 Jules Bianchi Marussia 1:18.518 +2.908 25 laps
19 Max Chilton Marussia 1:18.525 +2.915 19 laps
20 Marcus Ericsson Caterham 1:19.865 +4.255 23 laps
21 Kamui Kobayashi Caterham 1:20.227 +.617 14 laps
22 Esteban Gutierrez Sauber 1:22.388 +6.778 6 laps