Defending IndyCar champion Scott Dixon has finished fourth in the season opener in St Petersburg, Florida.
Australia's Will Power drove a convincing victory, beating American Ryan Hunter-Reay by almost two seconds.
Team Penske driver Power, who also won the Grand Prix of St Petersburg in 2010, has now won three straight races bridging the 2013 and 2014 seasons.
It marked his 22nd victory in 122 starts - although his strong finish last season wasn't enough to give him a first series title, with the 2013 championship went to Dixon.
"I'm pretty tired, mentally tired,'' said Power after holding off 2012 series champion Hunter-Reay in what turned into a 22-lap closing sprint following a caution re-start.
Starting from the second row on the grid, Power won by 1.9475 seconds on the 3km temporary street circuit.
Hunter-Reay overtook Power's teammate Helio Castroneves of Brazil on turn one of the 88th lap of the 110-lap race.
Castroneves, a three-time winner in St Petersburg and runner-up last year, was third.
Polesitter Takuma Sato of Japan led the first 33 laps, but finished seventh behind sixth-placed Tony Kanaan of Brazil.