INDIANAPOLIS—The Indianapolis 500 is new again.

Danica Patrick is a proven winner with a legitimate shot at taking the checkered flag, all the top teams and drivers are back for the 92nd running of the Indy 500 and optimism is high for what should, for the first time in 13 years, truly be “The Greatest Spectacle in Racing.”

Much of the optimism comes from the long-awaited unification of the two American open-wheel series in February.

Pointing to the strong mix of experienced drivers and young talent at Indy, longtime team owner Roger Penske said he’s excited...