Penske were in predictably strong form as the weekend's activities got underway ahead of the Honda Indy Toronto, the tenth round of the 2015 Verizon IndyCar Series.
Juan Pablo Montoya had a comfortable edge over his team mate Simon Pagenaud in the first 40 minute practice session on the 11-turn, 1.755-mile temporary street course, setting a top time of 1:00.6343s (104.198mph) to put him 0.1579s clear of the rest of the field.
CLICK: Full practice 1 times from the streets of Toronto.
Gil de Ferran holds the qualifying record for Toronto with a one-lap best of 57.143s (110.565mph) set all the way back in July 1999.
The session had got off to a slightly late start because of earlier delays in the schedule of on-track activities. Pagenaud set the early fastest lap of the morning but was unable to hold off Montoya in the final minutes.
CFH Racing's Josef Newgarden was third fastest just ahead of a strong showing from team mate Luca Filippi and KVSH Racing's Sebastien Bourdais who was able to finish just ahead of the second brace of Penske drivers with Will Power sixth fastest just ahead of Helio Castroneves.
Rahal Letterman Lanigan Racing's Graham Rahal was the highest-placed Honda runner, and the only one from the Japanese manufacturer to crack the top ten in the timesheets by the time the chequered flag called time on proceedings.
"It's always a very tricky course because the amount of concrete-to-pavement transitions on the track is a really difficult thing to get a handle on," explained Rahal. "I think we are up to the task, for sure, but I always find this track difficult because of the variation in speed of the corners and the bumps that exist mid-corner due to pavement changes."
Having got off to a late start, the session was also curtailed by five minutes because of a red flag for Ganassi's Scott Dixon who had stopped out on track. By the time the #9 had been retrieved, there was insufficient time for anyone to get back out for further runs.
Dixon finished the first practice as the 16th fastest of the 23 cars at work on the streets around Exhibition Place. Slowest of all was Rodolfo Gonzalez who has been recalled to action by Dale Coyne Racing for his fourth outing of the season. Gonzalez - who made his series bow at Alabama and going on to compete in both of the Dual in Detroit doubleheader races at the end of May - was the only one of the drivers not to reach the milestone of 100mph for a lap of the street circuit. His team mate this weekend, Tristan Vautier, was one place ahead of him in the final time sheets.
There will be a second 45-minute session this afternoon at 2.45pm local time (7.45pm BST) and a third on Saturday morning at 10.40am (3.40pm BST) before qualifying in the afternoon at 2.30pm (7.30pm BST) which will follow the usual three-round elimination format used by the series for street and road course events.
The 85-lap Honda Indy Toronto will get the green flag on Sunday afternoon at just after 3.30pm (8.30pm BST).
See full practice 1 times from the streets of Toronto.