Scott Dixon has claimed an explosive victory in the GoPro IndyCar Grand Prix of Sonoma as the hunt for the title remains in the balance following a frantic penultimate race.

The Ganassi stalwart Dixon beat Andretti Autosport’s Ryan Hunter-Reay with Schmidt Peterson Motorsports driver Simon Pagenaud claiming third.

Will Power had dominated the first portion of the race from pole position but spun at turn 7 on a restart which dropped him back to 20th.

Power then fought his way back through the field and tempted disaster on the final corner in a nail-biting scrap when he was sandwiched between Sebastien Bourdais and Justin Wilson before flashing over the line in ninth place.

However, after an investigation, Power was dropped to 10th after it was judged that his pass on Wilson had occurred under a local yellow flag.

Power, who led a race high of 33 laps, had been on the move on the 85th and final lap as he set about trying to scavenge valuable points.

“I was going for points and it looked like an easier target because Justin was very much struggling. But man it ripped the wheel out of my hand and I grabbed push-to-pass at the last minute,” Power said.

“I thought this is going to be interesting, three wide here. That was a hairy last corner.”

Power’s closest, Helio Castroneves, was involved in a multi-car turn 2 incident on the opening lap, which immediately neutralised any chances he had of fighting at the front before he finished 18th, one spot behind the luckless Ryan Briscoe.

“It’s a pretty disappointing finish, to be honest,” Castroneves said.

“The Hitachi Chevy was really fast all weekend and to get hit so early on in the race was really tough. That certainly put us behind, fixing the damage in the front and back of the car and it was tough to recover. 

“We are still in it and we know what we need to do now over the 500 miles.”

After going into the Sonoma weekend with a 39-point lead Power moves to a 51-point advantage over Castroneves while Pagenaud is 81 points away after gaining 11 points on the Australian.

A total of 104 points available at Fontana’s MAVTV race.

Hunter-Reay is 92 points off the lead in fourth place while Dixon is 103 points off Power.

Dixon’s victory after flashing through to take the lead with two laps remaining from Mike Conway, who had only just inherited first place from Graham Rahal, was the 35th of his career moving him to equal fifth all-time alongside Bobby Unser.

With Conway’s Carpenter Racing Chevrolet running on fumes at the end, the Briton crawled across the line in 14th place, small reward for what had been another stout drive.

Meanwhile Colombian Gabby Chaves (Belardi Auto Racing) has held on to take the Indy Lights title as Jack Harvey (Schmidt Peterson Motorsport) claimed a weekend double.

Harvey moved to four wins to equal Chaves however the latter claimed the title by virtue of five second place finishes compared with the Englishman’s sole runner-up effort.

Andretti Autosport’s Matthew Brabham finished his maiden year in Indy Lights with a fifth place finish.

See below for full results

See below for full points