By Steve Keating
Fighting to conserve fuel, Franchitti was able to cruise home with arms raised in triumph after compatriot Mike Conway's car launched into the fence and disintegrated, bringing out the yellow flag with one lap to go.
In both his 500 wins, Franchitti crossed the finish line unchallenged. His first victory at the famed speedway came under caution in a rain-shortened race in 2007.
Despite the anticlimactic finish, there was no doubt among the 250,000 race fans at the sprawling speedway that Franchitti was full value for the win, the Scotsman delivering a flawless drive in scorching conditions to become just the 17th man to register two 500 victories.
With two trips to Victory Lane in four years, Franchitti's place among the Brickyard greats is secure but the Scotsman refused to put himself in the same league as his childhood idols.
"They showed me a list of two-time winners, those guys are legends," Franchitti told reporters. "I'm just a driver, those guys are legends.
"I could win races, Indy 500s, for the rest of my life, until I'm 70-years-old and I still wouldn't be in the same vein as Jim Clark and Jackie Stewart.
"I'm in awe of both of them."
Dan Wheldon made it a British one-two when he crossed second for the second consecutive year.
A third Briton in Alex Lloyd appeared to have completed the podium until race officials awarded Marco Andretti third place after reviews showed the American had slowed for the pace car when the yellow flag came out and was passed by several cars.
Back in Indy Cars after a brief and unsuccessful stint in NASCAR, Franchitti staked his claim to the race early by charging from third to first on the opening lap.
The Briton led 93 of the first 100 laps, many of them with Brazil's Helio Castroneves filling his rearview mirror.
Chasing a record-equaling fourth 500 win, Castroneves ran a cool, cagey race to stay in touch with the leaders as he positioned himself for the sprint to the finish.
The Brazilian's hopes were dashed, however, when he stalled in his final pit stop, an uncharacteristic error that saw him fall back to 16th.
Franchitti held steady as his challengers faltered, fending off a charging Wheldon until Conway's crash ended the suspense.
With victory secured, Franchitti jumped out of his car into the arms of his actress wife Ashley Judd and chugged from the traditional bottle of milk in Victory Lane, even as the crowd at the far end of the speedway watched quietly when Conway was removed from the mangled cockpit of his demolished car.
Conway was examined at the speedway clinic and then airlifted to hospital but officials said his injuries were not life-threatening.
"This tastes just as good the second time," said Franchitti, wiping the milk from his face. "I have to say that feeling when you drive into Victory Lane, you see some of my family, my dad, Ashley, my friends from Scotland, my team ... it's cool.
"You get out and you get a drink of milk. That's what it's all about."
Franchitti's win earned team owner Chip Ganassi a unique 500 double as the first man to win the United States' two biggest races, the Daytona and Indy 500, in the same year.
"I think it says a lot about Chip ... all he wants to do is win," said Franchitti. "If you're not interested in that, if you take your eye off the ball, he lets you know.
"That's all he cares about. We go racing and we like to win."
(Editing by Dave Thompson/Ian Ransom)