Penske's Newgarden and Power admit 2018 IndyCar title bids over

Power and Newgarden locked out the front row but ended the day classified 21st and 10th respectively, and now lie joint third in the championship on 511 points - 87 points behind leader Scott Dixon with 104 available in the double-points Sonoma finale.

A gearbox issue, a mid-race crash and a pitlane speeding penalty left Power seven laps down at Portland.

Newgarden led in the middle of the race before his strategy was undone by a full course yellow that put him down in 17th after a pitstop.

"We led some laps and I think we had a [car] that was good enough to win it," said Newgarden after recovering to 10th.

"It just didn't fall our way. You can't predict these IndyCar races.

"I wish we could get Lady Luck on our side one of these days. It just seems to walk away from us of late. Dixon was able to take advantage of it."

At the start of the race it looked like the Penske drivers and second-in-the-championship Alexander Rossi would all make inroads on Dixon's lead as the Ganassi driver was caught up in a first-lap crash.

But Dixon was able to recover to fifth place.

"Those guys are having a great year and luck falls on their side," said Newgarden of Dixon.

"Now we will just go and try and win the season finale and do what we can.

"I don't think we have much of a shot at the championship. We've given it a good effort here at Team Penske and you can't ask much more out of the team."

Poleman Power said his gearbox problems had begun before the race even started.

"On the warm-up lap before the green, something happened to the gearbox," he explained.

"It jumped to neutral, I went into emergency mode and made it go into gear and thought, 'OK, that's alright.'

"Then, coming out of the hairpin on the first restart, it popped into neutral again and everyone behind me went past. Then I realised I couldn't use first gear.

"We were on a reasonable strategy and I made a mistake trying to keep [Matheus] Leist behind me. Then, the gearbox completely went.

"I'm not sure the gearbox would have made it the whole race, anyway.

"Man, it's a tough sport. It's too bad because it was actually going to be a reasonable day.

"Now, we just go to Sonoma, have fun and hopefully have a good day, have a good finish to the year."

For Power or Newgarden to win the championship, they would now need to score the maximum 104 points at Sonoma, with Dixon finishing 22nd or worse and Rossi ninth or worse.