As it turned out, he couldn't have done anything more.
Dixon won the season-long fight, earning his second series title with a second-place finish in the Peak Antifreeze & Motor Oil Indy 300 at Chicagoland Speedway, a race in which he only had to finish eighth. But Castroneves won the final round in thrilling fashion, starting from dead last, leading the most laps and edging out Dixon at the line by fewer than 13 inches (.0033 seconds) in a gratifying finale to a season full of frustration for the Team Penske No. 3.
"I'm kind of speechless," Castroneves said. "For everything that happened, the whole season, having such a hard time. Obviously we've been very consistent. If it had been normal circumstances, I'd have to say we'd be the champion today."
Under such circumstances, a season with two wins, a record eight runner-ups and an average finish of 4.0 would be enough for a championship that has eluded the two-time Indianapolis 500 winner. But Target/Ganassi Racing's Dixon had a superb season, with six wins and 11 podium finishes through 14 races, giving him a 78-point cushion with three races to go.
The chase could have, even should have, been over at that point, but Castroneves fought back with a win at Sonoma, Calif., and a second at Belle Isle in Detroit. He never stopped pushing, perhaps too much in the case of Belle Isle, where he was penalized for blocking Justin Wilson and forced to give up the lead, a chance at victory and 10 more crucial points.
His push continued Saturday in qualifying, as he was ruled to have gone below the white-lined boundary at the bottom of the track "numerous times" and had a fourth-place qualifying effort nullified. He was relegated to the back of the field, in 28th.
Castroneves didn't stay there long. He was in 18th place on Lap 3, 12th place on Lap 11, in the top 10 by Lap 32. On Lap 59 he passed Danica Patrick and Dan Wheldon in one swoop in Turn 1, moving him up to fourth -- his pre-penalty starting spot.
On Lap 78 he took the lead for the first time when his Team Penske pit crew sent him off pit road first on a yellow-flag stop. He would end up leading a race-high 80 of the next 123 laps.
"We did everything we could do today," said Tim Cindric, Penske Performance president. "You can go home and hang your head proud when you know you did whatever you could do to lead the most laps, win the race. The rest of it was just a matter of destiny from there.
"Helio never gives up. He was upset yesterday [after the qualifying penalty], but he gets over that. He knew his job was to stay clean and put himself in a position to do well. The biggest thing to do was make sure he knew that he didn't have to do it all in the first lap."
Once Castroneves was in sight of the lead, he didn't settle for anything less.
"Cindric was telling me to save fuel, save fuel," Castroneves said. "I'm like, 'Look, I need to go to the front because I don't want to lose that pack. We were able to save fuel, do what we were able to do.
"When we got to the lead it was like, 'OK, now we just have to stay here.' So through that whole situation, I kept cool. I was pretty under control, not having any issues at all. We [adjusted] the car a little bit not in the pit stops but at least inside the cockpit. Other than that, it was an exciting run."
Exciting? Castroneves and Dixon sprinted to the checkered flag side-by-side, with the initial scoring giving Dixon the win. Castroneves parked his Dallara-Honda on pit road and began the walk to Victory Lane and his second-place spot on the podium, lamenting "the story of our season, second place." Then just before he got to the Victory Lane gate, he was informed that victory was his via photo finish.
The news arrived too late for his trademark frontstretch fence climb, but he didn't enjoy it any less.
"I knew it!" he exclaimed after seeing a slow-motion replay from the finish line. "We tried everything to win."
That "we" extended to the No. 6 of Ryan Briscoe, tucking in behind Castroneves in the waning moments to provide the last burst of aerodynamic push that made the difference.
"I knew while Dixon was in front, Helio couldn't win the championship. But whether it was the last race of the championship or the first, in that position, that's what a teammate's got to do," said Briscoe, third in the race and fifth in points. "It was great that it actually paid off and Helio crossed that line just in front of Scott. What a wild race."
Few in series history have been wilder. The margin at the finish was the second-closest in series history (Sam Hornish Jr. beat Al Unser Jr. in 2002, also at Chicagoland, by .0024 seconds) and Castroneves' march from 28th bettered the 26th starting spot Buddy Lazier won from in Phoenix in 2000.
It wasn't enough for a title. But it was more than enough to end the season on a high note.
"Coming from the back, we proved that we kept the three C's together: calm, cool, collected. Our plan, we executed," Castroneves said. "Just unfortunately Ganassi and Scott, they were right there. We did our part.
"Hopefully next year we start like that and finish just a little better in the championship."
John Schwarb is a motorsports contributor to ESPN.com. He can be reached at firstname.lastname@example.org.