REUTERS: Alex Palou pounced on a late restart when leader Josef Newgarden suffered engine trouble to win the IndyCar Grand Prix Road America on Sunday while former Haas Formula One team mates Kevin Magnussen and Romain Grosjean reunited on the starting grid.
Polesitter Newgarden had looked poised to give Team Penske their first win of the season until his car, with two laps to run, suddenly lost power during a restart following a late caution, allowing Palou to shoot past him into the lead and gifting the young Spaniard and Chip Ganassi Racing the win.
Colton Herta took second for Andretti Autosport ahead of Penske's Will Power.
Reigning series champion Scott Dixon of New Zealand was fourth while Grosjean continued to shine in his maiden IndyCar season, the Frenchman finishing fifth for his second top-five result in the last four races.
The second win of the season for Palou moved him to the top of the IndyCar drivers championship, 28 points in front of Mexico's Pato O'Ward, another of IndyCar's emerging young drivers with two wins this season.
Grosjean and Magnussen, who for four years were team mates at Haas before both were let go by the F1 outfit at the end of last season, were reunited at the Wisconsin track.
While Grosjean is running a full season with Dale Coyne Racing and already has a second-place finish, Magnussen made his IndyCar debut, filling in for Felix Rosenqvist at Arrow McLaren after the Swede was injured in crash last Saturday in Detroit.
Magnussen, who made 119 Formula One starts for McLaren, Renault and Haas, qualified 21st of 25 cars but led for six laps through the midway part of the race before retiring with mechanical issues with 15 laps to go.