Dixon's Target Ganassi teammate Dario Franchitti won the race. Dixon's race was damaged when a slow pitstop dropped him to 22nd from sixth.
There was more bad news for Dixon after the race following a video review that showed three cars illegally passed Marco Andretti under caution in the race's final lap.
The unofficial results showed Andretti finished sixth behind winner Dario Franchitti. He was moved up to third behind England's Dan Wheldon more than two hours after the race when IndyCar officials ruled Alex Lloyd, Scott Dixon and Danica Patrick did not have the right to pass Andretti as the field strolled to the finish.
Alex Lloyd moved down one spot to fourth. Scott Dixon moved from fourth to fifth, and Danica Patrick dropped from fifth to sixth after the league nullified the passes they made after the caution flag came out on Lap 199.
Winner Franchitti drove 199 nearly flawless laps, then survived the last one with a huge break from a spectacular crash for his second win at the Indianapolis 500.
Two years removed from a failed try in NASCAR, Franchitti held on with a scant tenth of a gallon of fuel left in the tank - a victory made possible by a crash that sent Mike Conway airborne and into the wall, and left the final lap to be run under a caution flag.
Conway, who waved to the crowd as he was being taken off the track, was airlifted to the hospital with an injured leg.
"Still running," the winner told his crew over the radio as he crossed the finish line, while wreckers were moving out to scoop up debris from Conway's accident with Ryan Hunter-Reay.
The victory made Franchitti's boss, Chip Ganassi, the first owner to win Indy and NASCAR's Daytona 500 in the same year. It also validated the Scottish driver's return to the IndyCar circuit two years after celebrating his 2007 Indy victory by making an unsuccessful move with Ganassi to NASCAR.
