Highcroft Acura's David Brabham and Scott Sharp extended their American Le Mans Series LMP1 lead with an ultimately comfortable win over an ailing De Ferran Acura at Mosport Park.
Sharp was unable to hold on to his pole advantage at the start as Gil de Ferran and Intersport's Jon Field pushed him back to third.
Plucky privateer Field then attacked de Ferran, twice nosing into the lead during a frenetic opening stint. But his giantkilling run was shortlived, as a problem at the front of the car brought Field into the pits after just eight laps.
De Ferran was left with a comfortable lead over Sharp, who had his hands full fending off Marino Franchitti's LMP2 Dyson Lola-Mazda.
The flying Franchitti overtook Sharp to run second overall - which became a shock race lead after half an hour when de Ferran made the first of a string of pitstops to attend to low gearbox oil. Radio failure led to confusion in the stop, with de Ferran initially trying to get out of the car before being discouraged by his crew, and then going off the road on his out-lap.
De Ferran's problems also accounted for Franchitti, as the Scot's windshield was covered in oil from the Acura as it went off ahead, forcing Franchitti to back off and then pit earlier than planned.
That left Sharp and Brabham free to take a comfortable victory, with de Ferran and Simon Pagenaud nursing their car home for second, two laps adrift.
Third and LMP2 victory ultimately went to Adrian Fernandez and Luis Diaz, allowing the Fernandez Acura duo to clinch the class title -- despite Dyson having been quicker for most of the weekend.
The Chris Dyson/Guy Smith car had a heavy crash just before the one-hour mark, but Franchitti and team-mate Butch Leitzinger fought back to challenge Fernandez, getting ahead when the Mexican was penalised for pitlane speeding.
He recovered and closed back onto Leitzinger's tail, picking up the lead when the Lola-Mazda expired in a cloud of smoke with less than 15 minutes to go.
Corvette claimed its first GT2 win, with Jan Magnussen fending off a huge challenge from Risi Ferrari's Pierre Kaffer to clinch victory for himself and team-mate Johnny O'Connell.
The two Corvettes had hit the front early on, while Risi's Jaime Melo and Kaffer charged into contention following the Saturday crash that had left the Ferrari at the back of the grid.
Risi got ahead at the first pit stops, only to fall back behind both Corvettes when getting out of the way of a prototype shortly afterwards.
Kaffer repassed Magnussen for second, then retook the lead when Olivier Beretta had a quick trip off the road.
But it was Magnussen who emerged in front following the final pit visits, determinedly resisting all Kaffer's passing attempts as he rejoined just ahead on cold tires. The battle raged throughout the closing stages, with Magnussen clinching the win by just 0.3sec.
Beretta and Oliver Gavin completed a great day for Corvette with third, just ahead of the Farnbacher Loles Porsche.
Having dominated class qualifying, Rahal Letterman BMW's race fell apart early. Unfounded puncture fears prompted the #92 entry to pit prematurely, and it later retired with engine problems, while the #90 car was delayed by contact with the #45 Flying Lizard Porsche.