Sebastian Vettel edged out Fernando Alonso to set the fastest time in a very close final Canadian Grand Prix practice session in Montreal.
Just 0.006 seconds split Vettel's Red Bull and Alonso's Ferrari, with Lewis Hamilton taking third for McLaren, and Mark Webber (Red Bull) and Pastor Maldonado (Williams) completing the top five.
The session had seen plenty of activity at the top of the timesheets even before the late switches to super soft tyres. Jenson Button's McLaren emerged ahead once the early runs had been completed, but he was soon usurped by Vettel, who set benchmarks of first 1m15.440s then 1m15.022s to sit in first place at the mid-way point.
Alonso beat him soon afterwards, clocking a 1m14.737s despite locking up into the final chicane, although the Ferrari's time in front was very short-lived as Hamilton went 0.025s quicker mere seconds later.
Continuing the close action, when Vettel reclaimed the top spot with 16 minutes to go, his 1m14.711s was just 0.001s faster than the McLaren.
As more and more drivers moved onto super softs, Alonso was the first to really exploit their potential with a 1m14.448s nine minutes from the chequered flag.
That held up until Vettel came through a scant 0.006s faster six minutes later. The German turned traffic into an advantage as he grabbed a tow from Michael Schumacher's Mercedes. Vettel then went quicker still in the first two sectors on his final lap before lost time in the final part of the lap, although his existing 1m14.442s was sufficient to secure first position.
Two drivers will go into qualifying with no Saturday running at all. Nico Rosberg's Mercedes cut out and parked on track on a very early installation lap, while Toro Rosso's Jean-Eric Vergne ended up parked in the Turn 2 tyres after making a mess of Turn 1 on his first flying lap.
There may be issues for Kimi Raikkonen as well, with the Lotus driver under investigation for making a last-minute swerve into the pitlane after a mistake at the final chicane.
Just 1.056s covered the top 16 cars, as the Montreal times remained typically close. Behind the leaders, Felipe Massa maintained his encouraging form for Ferrari in sixth, followed by Schumacher, Lotus duo Romain Grosjean and Raikkonen, and Force India's Nico Hulkenberg. Jenson Button was only 15th for McLaren and expressed concern about brake balance issues over the radio.
Pos Driver Team Time Laps
1. Sebastian Vettel Red Bull-Renault 1m14.442 22
2. Fernando Alonso Ferrari 1m14.448s + 0.006 17
3. Lewis Hamilton McLaren-Mercedes 1m14.712s + 0.270 19
4. Mark Webber Red Bull-Renault 1m14.724s + 0.282 21
5. Pastor Maldonado Williams-Renault 1m14.755s + 0.313 22
6. Felipe Massa Ferrari 1m14.767s + 0.325 21
7. Michael Schumacher Mercedes 1m14.796s + 0.354 19
8. Romain Grosjean Lotus-Renault 1m14.873s + 0.431 20
9. Kimi Raikkonen Lotus-Renault 1m14.977s + 0.535 21
10. Nico Hulkenberg Force India-Mercedes 1m14.992s + 0.550 22
11. Paul di Resta Force India-Mercedes 1m15.067s + 0.625 19
12. Sergio Perez Sauber-Ferrari 1m15.112s + 0.670 21
13. Kamui Kobayashi Sauber-Ferrari 1m15.126s + 0.684 24
14. Bruno Senna Williams-Renault 1m15.237s + 0.795 22
15. Jenson Button McLaren-Mercedes 1m15.327s + 0.885 22
16. Daniel Ricciardo Toro Rosso-Ferrari 1m15.498s + 1.056 19
17. Vitaly Petrov Caterham-Renault 1m16.268s + 1.826 24
18. Heikki Kovalainen Caterham-Renault 1m16.545s + 2.103 20
19. Pedro de la Rosa HRT-Cosworth 1m17.705s + 3.263 21
20. Timo Glock Marussia-Cosworth 1m17.974s + 3.532 23
21. Narain Karthikeyan HRT-Cosworth 1m18.189s + 3.747 21
22. Charles Pic Marussia-Cosworth 1m18.684s + 4.242 23
23. Jean-Eric Vergne Toro Rosso-Ferrari no time 3
24. Nico Rosberg Mercedes no time 1
All Timing Unofficial