Dario Franchitti benefited from perfect pitstop and yellow timing to win an incident-packed IndyCar race in Toronto for Ganassi.
Penske team-mates Ryan Briscoe and Will Power's strategies helped them complete the podium despite both picking up punctures in a messy first lap.
But there was heartbreak for the Canadian crowd, who for a while appeared set to celebrate an incredible one-two for part-time racers Alex Tagliani (Conquest) and Paul Tracy (KV). Ultimately Tracy retired after a collision with Helio Castroneves (Penske) as they fought for second, and the yellow that worked perfectly for Franchitti's final stop ruined Tagliani's strategy.
A wild start saw Graham Rahal and Power make contact even before the green, puncturing the Penske driver's tyre and breaking the Newman/Haas/Lanigan car's front wing, with Briscoe also collecting a puncture as the pack jostled through the mess.
Franchitti held his lead, ahead of the fast-starting Tagliani, and the polesitter proceeded to edge away from the field through the opening laps, which were interrupted by brief yellows for a tangle between Dan Wheldon and Richard Antinucci, and a spin for Ed Carpenter.
The leader opted to make his first pit visit on lap 25, losing time with a slow wheel change, while Tagliani chose to stretch his fuel mileage and run to lap 31.
He ended up leading a Canadian one-two for several laps. Tracy had carved from 15th to eighth on the first lap, then picked up further places as several drivers ahead chose to pit under the early yellows.
Dive-bomb passes on first Mike Conway, then Scott Dixon brought Tracy onto Tagliani's tail, where he remained until they pitted.
As the strategies played out, Dreyer & Reinbold's Tomas Scheckter emerged in the lead for a spell, under pressure from Penske's Castroneves and Power, the top two among the drivers who had pitted under the early yellows, and all three trying to stay out long enough to make just one more stop before the flag.
They succeeded, and as the pitstops cycled through, the Canadian one-two was resumed, but only briefly before a tangle between Rahal and the lapped Carpenter brought out another yellow just as the rest of the field were in the process of making their stops.
This was ideal timing for Franchitti, who was in the pits at that moment and emerged second behind Castroneves, and ahead of Tracy, who had pitted just before the caution but had a slow stop. However, the yellow was bad news for Tagliani, who was still leading and had to wait until the field formed up before making his stop, dropping him to ninth.
Franchitti was all over Castroneves when racing resumed, eventually passing the Brazilian as he slid a little wide at Turn 1.
But when Tracy tried to take second from Castroneves at Turn 3 next time around, contact was made between the pair, squeezing Tracy into the Turn 4 wall and breaking Castroneves' suspension.
Further carnage followed in the ensuing laps, with Tony Kanaan sustaining broken suspension, Mario Moraes tangling with EJ Viso, and then Tagliani and Scheckter colliding at Turn 3 and collecting Moraes' already battered car in the process.
Once things had settled down, Franchitti reeled off the final laps ahead of Briscoe, Power and Dixon, the latter pair having both passed Justin Wilson late on - Power taking advantage into Turn 3 after the Watkins Glen winner had lost momentum trying to pass Briscoe at Turn 1. Dixon then pounced at the final restart, completing a damage limitation drive after he had been caught in the same situation as Tagliani at the last stops. Prior to that, the champion had been stalking Tagliani and Tracy and looking set to challenge them for victory.
Andretti Green's Danica Patrick came through to sixth, ahead of a breakthrough seventh place for Ryan Hunter-Reay (Foyt). Tagliani resumed after his collision to take ninth behind Marco Andretti (AGR).
Conway's challenge for a podium ended when he hit the wall just after being overtaken by Tracy, while Robert Doornbos was also a top four factor until his Newman/Haas/Lanigan car's gearbox packed up.
The result puts Franchitti back into the championship lead by two points over Dixon.
Pos Driver Team Gap 1. Dario Franchitti Ganassi 1h43m47.1408 2. Ryan Briscoe Penske + 1.6745s 3. Will Power Penske + 2.1355s 4. Scott Dixon Ganassi + 2.4803s 5. Justin Wilson Coyne + 2.9230s 6. Danica Patrick Andretti Green + 6.4095s 7. Ryan Hunter-Reay Foyt + 7.1837s 8. Marco Andretti Andretti Green + 8.2552s 9. Alex Tagliani Conquest + 13.4745s 10. Raphael Matos Luczo Dragon + 16.0983s 11. Mario Moraes KV + 19.0141s 12. Hideki Mutoh Andretti Green + 1 lap 13. EJ Viso HVM + 1 lap 14. Dan Wheldon Panther + 1 lap 15. Ed Carpenter Vision + 3 laps Retirements: Tomas Scheckter Dreyer & Reinbold 74 laps Tony Kanaan Andretti Green 70 laps Helio Castroneves Penske 65 laps Paul Tracy KV 65 laps Graham Rahal Newman/Haas/Lanigan 57 laps Richard Antinucci 3G 41 laps Mike Conway Dreyer & Reinbold 32 laps Robert Doornbos Newman/Haas/Lanigan 26 laps