Rahal won the pole earlier in the day with his Honda-powered auto and became the seventh IndyCar driver to win the first seven races of the year.
It was Graham Rahal's first pole since 2009 when he competed with Newman/Haas/Lanigan and it's the first pole for the Rahal/Letterman/Lanigan team since Scott Sharp won the top spot at Texas in 2007.
A day after his wife's dragster exploded in a ball of fire in an NHRA event, IndyCar driver Graham Rahal dominated the first leg of the Detroit Grand Prix doubleheader Saturday, winning the IndyCar Series' 70-lap race from the pole. Rahal's Rahal Letterman Lanigan Racing-Honda topped the first group with a 1min13.9681sec lap on his final attempt to beat Indy 500 Takuma Sato's Andretti Autosport-Honda by 0.0747sec. "I just didn't want to mess up".
Behind came James Hinchcliffe of Schmidt Peterson Motorsports-Honda, followed by the three Penske-Chevrolets of Simon Pagenaud, Josef Newgarden who made a tactical blunder by starting on reds when the track was at its slowest and then switching to blacks.
Alexander Rossi, the 2016 Indy 500 victor, and this year's Indy 500 victor Takuma Sato make up the second row.
"Kudos for Honda for sweeping in the podium", Dixon said.
Graham Rahal drives through the second turn during the first race of the IndyCar Detroit Grand Prix auto racing doubleheader, Saturday, June 3, 2017, in Detroit.
Castroneves' second-best lap in the No. 3 Hitachi Team Penske Chevrolet of 1:14.0414 was still good enough to be fastest in his group, so he will start outside Rahal on Row 1 in this afternoon's race.
The second Dual in Detroit race is set for Belle Isle Sunday afternoon, with the green flag expected to unfurl at 3:30pm.
For complete race information check out the IndyCar website.