New Zealand driver Scott Dixon is relaxed despite trailing his leading rivals on the grid for the deciding race in the IndyCar series.

Dixon will win a fifth series crown if victorious in today's closing event at Sonoma, California.

However, the Chip Ganassi Racing driver will need to do it from sixth on the grid and see off a challenge from four Team Penske drivers still all mathematically in contention.

At the head of that list is series-leading American Josef Newgarden, who broke the track record three times in claiming pole position.

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Newgarden, chasing a maiden series title, picked up a point for his qualifying efforts to sit four in front of second-ranked Dixon heading into the double-points race.

Behind Newgarden on the grid are three team-mates, in order: Australian Will Power, France's Simon Pagenaud and Brazil's Helio Castroneves. All could claim overall honours if results fall their way.

Dixon was wary of his car's speed limitations but he has a good history at the race and believes strategy will play an important role.

"The Penske group are fast here, and it's exactly what we expect, but the race is going to be interesting," Dixon said. "We can make it work."

Dixon's most recent title in 2015 ended with a victory at Sonoma after starting ninth on the grid. He tied with Juan Pablo Montoya in the standings and won the championship on a tie-breaker. Kiwi drivers Brendon Hartley and Earl Bamber have all but wrapped up the World Endurance Championship title after notching a fourth successive win.

Hartley, Bamber and German Timo Bernhard powered their Porsche hybrid vehicle to victory at the United States leg of the series in Texas to open up a commanding lead.

The trio have racked up wins at Le Mans, Nurburgring and Mexico to open a cavernous advantage back to their nearest rivals from Toyota.

It would take a catastrophe in the final legs in Japan, China and Bahrain to prevent victory.

- AAP