Scott Dixon denies Juan Pablo Montoya 2015 IndyCar title at Sonoma

Ganassi driver Dixon came into the weekend third in the points and needing to win the race and hope that season-long championship leader Montoya encountered some sort of problem.

He took care of the first part, reeling off a perfect performance on an afternoon where fuel mileage and rapid tyre wear made for a tangle of strategies.

And incredibly, Penske took care of the other part for him. Will Power had been in command of the early part of the race, with Montoya running around in the middle of the top 10, which at that point was enough to preserve his points lead.

His afternoon took a dive shortly after a restart, when Power, running just ahead of Montoya, appeared to leave a gap at the top of the hill.

Montoya went to fill it, only for Power to rejoin the racing line, leaving his team-mate with nowhere to go other than into his rear.

The impact sent both cars back into the pits for repairs, and Montoya rejoined near the back of the field and knowing that he needed to climb back to fifth in order to salvage the title.

Off-strategy cars cycling through their stops helped the Colombian to regain some places, but his best chance came at the expense of the driver who'd come into the weekend as his closest rival: Graham Rahal.

The Rahal Letterman Lanigan driver was fighting with Sebastien Bourdais when the Frenchman missed his brake marker completely at the hairpin and punted Rahal squarely in the rear, spinning him to the back of the pack.

That took Rahal out of the equation for Montoya and the resultant drive-through for Bourdais moved the Colombian up one more place to sixth, which put him equal on points with Dixon, but needing to gain one more place to avoid losing the title on a countback.

The next driver, Ryan Briscoe, was 3.0s down the road, and struggling on the red tyres, but with just 12 laps left, catching and passing the Schmidt driver was always going to be a tall order.

Montoya did manage to whittle the deficit down to 1.1s, but couldn't get any closer. After leading the championship for the entire year, he lost it by a single position as Dixon claimed a fourth title.

"We knew at the start of the weekend the title was still a chance and that's what we were hoping for," said an elated Dixon.

"This is fantastic. I don't know what to say. "Thoughts and prayers first to Justin Wilson's family.

"We were such a long shot to win it, and we won it on countback. I can't believe it."

Montoya refused to blame his team-mate after the race, instead shifting his disappointment to the double-points format.

"It doesn't matter what happened," he said "It's just a shame. We threw the championship away.

"We had a competitive car to do what we needed to do, and we didn't do it.

"When you have a double-points race at the end, it doesn't matter what you do all year - we had one bad weekend and we lost the championship."

Ryan Hunter-Reay ran towards the front all day to secure second, while a similarly solid afternoon from Charlie Kimball was rewarded with the final podium place.

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