Montoya, the IndyCar points leader, posted a one-lap time of one minute 0.643 seconds in the morning session over the 1.755-mile, 11-turn Exhibition Place street circuit. That stood as the day's fastest effort as rain washed out the afternoon practice run.
Montoya wasn't expecting such a good opening result.
"No, because we didn't do that many laps and we had a problem with the brakes so we had a little bit less track time," he said. "We went out there and the speed was there, which is encouraging.
"With the rain, it makes it harder because any rubber we put down (will be washed away). So (on Saturday) we have to start from zero again . . . but being that fast on a street course despite not running that much, that's pretty good."
The final practice is scheduled for Saturday morning before qualifying begins later in the afternoon. Gil de Ferran holds the track qualifying record of 57.143 seconds set in 1999.
The Honda Indy Toronto race goes Sunday afternoon.
Montoya currently leads the driver's standings with 348 points, having also registered two victories so far this season. He's 35 points ahead of Penske teammate Will Power, the defending series champion, and holds a 43-point advantage over Scott Dixon, three times IndyCar's top driver.
Power has a win and four pole positions on the season while Dixon has registered a victory and a pole.
However, Montoya says the only race he's concentrating on is the one on the track each weekend.
"You can't focus on points," Montoya said. "You have to focus and execute every weekend and if things work out well then we look good.
"So far it has been a good season. I think we have a really good car here in Toronto so we'll see."
Power, who was sixth in practice with a time of 1:00.8656, said battling a teammate for the driver's title does create an interesting scenario.
"Yeah, I mean, obviously battling teammates is a little bit harder because you're in the same engineering office," the Australian said. "Battling another team is a big team effort and the push is to beat that team but battling a teammate . . . it's a different story."
Penske's Simon Pagenaud had the second-best practice time (1:00.7922) while Josef Newgarden was third (1:00.8363). Luca Filippi (1:00.8500) and Sebastien Bourdais (1:00.8620) rounded out the top-five finishers in the 23-driver field that includes no Canadians.
James Hinchcliffe of Oakville, Ont., who is recovering from a serious leg injury sustained last month, will serve as the grand marshal of Sunday's race.
With no rain in the weekend forecast, Montoya predicted much faster times in qualifying Saturday.
"Oh yeah, we'll go higher," he said. "Qualifying will be at least a second and a half quicker than that."
And teammate Helio Castroneves, fourth in the driver's standings with 286 points and seventh in practice, said the closeness of the field Friday suggests a close qualifying session. The top 11 cars were separated by just a half second while the gap between Newgarden and eighth-place finisher Graham Rahal was under a 10th of a second.
"It's very tight," Castroneves said. "Third to ninth is in the same 10th, which is amazing.
"So it's definitely going to be competitive."
Castroneves, who captured the pole for the 2000 Toronto race, said the corners on the track present a formidable challenge for drivers.
"Most of the corners have a patch of concrete in the middle," he said. "It's actually an old concrete so it's almost like glass so when you hit the concrete it's very, very slippery.
"You go from asphalt to concrete to asphalt so you can figure what we have to deal with (on corners)."