Key Points:

Relief as much as elation coursed through Scott Dixon's veins after claiming his second IndyCar Series crown in Chicago today.

The beaming New Zealand driver clutched a US$1 million ($1.49m) cheque for winning the 17-race series, the perfect end to a year in which he won the glittering Indy 500 and married Emma Davies.

He was denied a series-record seventh race win this season when pipped into second place today by Brazilian Helio Castroneves in the Peak 300 at the Chicagoland Speedway.

But it wasn't enough to deprive the Auckland 28-year-old of the title he last won in his rookie season, five years ago.

He couldn't help but reflect as he wiped off the traditional cream pie that had been rammed in his face by Target Chip Ganassi teammate Dan Wheldon in the victory circle.

"The year on a whole has been amazing, an unforgettable year," said Dixon, who won the 2003 title.

"Getting married, winning the 500, winning a championship in one year - not too many people can probably say they've done that."

Actually, the last four Indianapolis 500 winners had gone on to win the series title but that mattered little for Dixon who revelled in his latest achievement in the rich American series.

The finish provided dramatics of its own, with Castroneves winning by 0.0033 of a second, the second-closest recorded win in the series' history.

However, this time the matter of inches didn't matter for Dixon, who last year ceded the title to Scot Dario Franchitti when he ran out of fuel two turns from the finish at the same circuit.

That memory and the way second-placed Castroneves had closed the series points margin from 78 last month to just 30 before today left Dixon relieved to have clung on.

His dominant form had faltered over the last three races.

"I think, unfortunately, we set our minds on having it (title) tied up a long time before now," Dixon said.

"I think that's what has run us into a bit of trouble. That was definitely the toughest two weeks I've had.

"Even today, you know, Helio wouldn't let it go. You got to take your hat off to him for doing all he needed to do."

The hard-charging Castroneves started 28th and last on the grid following an infraction in qualifying yesterday but sliced through traffic to lead the field after just 78 laps of the 200-lap race.

Even if Castroneves won, Dixon simply had to record a top-eight finish to clinch the series.

However, he gradually slipped from second on the starting grid to as low as 10th just after the halfway point.

Dixon kept his nerve, had faith in his car and team, who produced a superb late pit stop, to be wheel-to-wheel with the Brazilian over two memorable final laps.

The photo finish caused confusion post-race for nearly half an hour.

"It was the craziest victory circle I've been involved in where you see your car get rolled in position, you get out like you won the race, then they roll it out and say you haven't won it. That was tough to deal with," he said.

"But I think in the back of my mind we all knew we'd won the championship, and that was the main goal."

Dixon, frustrated with his title drought since 2003, said this title means more to him.

He was consistent all year, producing 14 top-five finishes in 17 starts as well as equalling Wheldon's six-win season record.

Dixon revealed pre-race that he had endured a disrupted buildup, having taken one of his dogs to the vet because it was suffering from ear ache.

"It was a bit of a pain but luckily enough the dog's doing well and we're all happy."

Castroneves, who finished the season with two wins and eight second placings, was excited to finally be told he won the race.

"I knew I won it, I knew," he said.

"We did everything we could. Scott Dixon and those guys they had a little better luck and they wound up winning the championship. Congratulations to them."