Juan Pablo Montoya was leading the championship heading into the final lap of the final race at Sonoma yesterday.
But with Dixon leading the race, and Montoya finishing sixth, the Kiwi driver collected double points at the season finale to pip the Colombian for the title on race wins countback.
Despite Dixon winning three races this season, and Montoya just two; the Team Penske driver said Dixon had just one good race.
"Dixon had a shit season all year and had one good race, and we paid the penalty," Montoya told Autosport.com.
"It sucks, but when you make the last race double-points on a road course and you change the tyre and you do everything you did for this weekend and you put so many variables, it doesn't even matter what you do all year," he added.
The Colombian hopes IndyCar reconsiders the double-points system for next season.
"We'll see if they [IndyCar] change it, but they like the excitement for the last race," he said.
"Is it fair? No, but we go into the last race of the year knowing it's a double points race.
"Is it fair for a normal championship? No, it's not fair, but it's the rules they want to play with, and if you don't like the rules, don't race."
