Louis Foster extended his championship lead to 77 points at the Gateway oval in St Louis, with only one round in the championship remaining.
Exclusive Autosport driver Foster, 19, entered the tricky short oval with three wins and a second place in the last four races in a run which has catapulted the British rookie into a strong position at the top of the series standings.
At Gateway last weekend he qualified third, and was part of a race long battle for a podium where he overcame understeer issues to finish fourth overall.
“It was quite a compact weekend,” said Foster, who is backed by Copart, a global leader in online auto auctions, and Florida-based luxury Italian garden umbrella brand Poggesi.
“We had a test day but I don’t think we got the most out of that, we had some car issues.
“So the whole weekend felt like learning and getting up to speed.
"Qualifying went pretty well, P3 certainly isn’t bad, I could have driven better in qualifying, I didn’t feel like I quite extracted the maximum from the car. I was a bit too safe on the first lap.
“I’d describe the race as OK. We had a lot of understeer in the car which made it quite tricky to follow other cars in traffic, which also made it hard if another car was able to get past and stay in front.
“Honestly it’s so hard to predict the temperature and how the track is going to react that sometimes you don’t quite get the balance right.
"Without any pitstops or time to make changes it was always going to be a struggle, but I’m proud of the result and the fact that I and the team extended our points advantage together.”
The championship clinch situation is complicated for Foster because there are bonus points on offer for pole, fastest lap and leading the highest number of laps, and how many cars start the final three races also impacts the points on offer.
A perfect score is 33 points per race, meaning there are a maximum 99 points on offer.
What Foster does know is that 23 points in total over the final three races will secure him a title in his rookie year racing in America where he has won on street and oval circuits, the likes of which he has not raced on before.
He isn’t thinking about any of that though.
“There’s no change in approach at Portland,” he said.
“I want to win races, I want to score pole positions and fastest laps, I want to end this season on a high for myself, all the people working so hard at Exclusive to put me in this position and any one who has helped to put me in this position.
“Whatever happens I have to thank them for their help and support.
“There’s three races to go, we’re 77 points in front. Anything can happen. It’s a good margin and it’s up to us to bring it home now.”
The Portland circuit in Oregon is a permanent road course 1.967 miles in length. Foster will race there on September 2-4.