FONTANA, Calif. — Scott Dixon won his first championship at 23, too young to appreciate what he had accomplished in his first full season with Chip Ganassi Racing and their first year in the IndyCar series.The next title five seasons later capped a dream year: Dixon won six races, including his only Indianapolis 500, got married, and topped it off with his second championship.Saturday night in the MAVTV 500, Dixon finished fifth to complete a remarkable rally for his third championship — five years after his last title, and 10 years after his first."This year I think has been far different, just in the fact midseason we didn't think we had a shot at the championship."Dixon, who has had five other top-three finishes in points, was seventh after the Iowa race in June, where an incident with then-leader Helio Castroneves made Dixon furious."I remember having a conversation with Helio after Iowa. I was like 'Man, you need to watch out. I'm not in the championship, don't do that again, because otherwise I can maybe hinder your championship,' " Dixon recalled Saturday. "It's funny how it turned out to be us fighting it out in the last few races."Dixon won the next three races, vaulted closer to Castroneves, and took the lead when Castroneves had mechanical trouble in both ends of a weekend doubleheader at Houston, where Dixon finished first and second."I can't take for granted the season we had. Yes, so close, but so far," Castroneves said.Dixon doesn't have to say that this time. American Le Mans: Neel Jani, Nicolas Prost and Nick Heidfeld won late Saturday at Road Atlanta in an LPM1 Lola in the final race in series history. The ALMS and Grand-Am will merge next year to form the United SportsCar Championship.