Will Power left it late on Friday to top the opening practice session around the streets of Detroit, with the Australian pacing the twenty-five-car field with a best time of 1:17.2768.
However, the rookies in the field all explored the limits of the bumpy Detroit circuit, with Romain Grosjean and Jimmie Johnson both spinning and Scott McLaughlin hitting the wall.
Grosjean, the pole sitter around the road course at Indianapolis Motor Speedway last month, spun his #51 Dale Coyne Racing machine at turn four, with his rear wing only grazing the barrier. He was able to keep going and ended the session thirteenth.
Johnson spun his #48 Chip Ganassi Racing machine around at turn three around the same time McLaughlin struck the barriers at turn five. The driver of the #3 Team Penske driver was the only one of the three rookies to see his session end there and then, with heavy damage to his front wing and suspension.
Chevrolet took the top three spots in the session, with Power’s late lap seeing him eclipse the best time of Sebastien Bourdais. The Frenchman endured a tough month of May and is looking for a strong second half of the season, and the driver of the #14 AJ Foyt Enterprises machine ended just 0.152 seconds behind Power.
Third was Arrow McLaren SP’s Pato O’Ward, while the leading Honda in the session was Scott Dixon in fourth in the #9 Chip Ganassi Racing machine, 0.341 seconds off the pace. Andretti Autosport’s Alexander Rossi rounded out the top five, just ahead of his team-mate Colton Herta, while Chip Ganassi Racing’s Marcus Ericsson was seventh.
Two-time series champion Josef Newgarden was eighth for Team Penske, while Ed Carpenter Racing’s Rinus Veekay and Andretti Autosport’s Ryan Hunter-Reay completed the top ten.
Current championship leader Alex Palou, who goes into the weekend knowing he will drop six places on the grid for Saturday’s opening race following an unscheduled engine change during the build-up for the Indianapolis 500, was only fifteenth fastest on his first visit to Detroit.
| POS. | NO. | DRIVER | NAT | TEAM | TIME/GAP |
| 1 | 12 | Will Power | AUS | Team Penske | 1:17.2768 |
| 2 | 14 | Sebastien Bourdais | FRA | AJ Foyt Enterprises | +0.1523 |
| 3 | 5 | Pato O’Ward | MEX | Arrow McLaren SP | +0.2375 |
| 4 | 9 | Scott Dixon | NZL | Chip Ganassi Racing | +0.3410 |
| 5 | 27 | Alexander Rossi | USA | Andretti Autosport | +0.3819 |
| 6 | 26 | Colton Herta | USA | Andretti Autosport | +0.5353 |
| 7 | 8 | Marcus Ericsson | SWE | Chip Ganassi Racing | +0.6960 |
| 8 | 2 | Josef Newgarden | USA | Team Penske | +0.7561 |
| 9 | 21 | Rinus VeeKay | NED | Ed Carpenter Racing | +0.8691 |
| 10 | 28 | Ryan Hunter-Reay | USA | Andretti Autosport | +0.9265 |
| 11 | 29 | James Hinchcliffe | CAN | Andretti Autosport | +1.2193 |
| 12 | 30 | Takuma Sato | JAP | Rahal Letterman Lanigan Racing | +1.2409 |
| 13 | 51 | Romain Grosjean | FRA | Dale Coyne Racing | +1.3084 |
| 14 | 7 | Felix Rosenqvist | SWE | Arrow McLaren SP | +1.4774 |
| 15 | 10 | Alex Palou | ESP | Chip Ganassi Racing | +1.5228 |
| 16 | 15 | Graham Rahal | USA | Rahal Letterman Lanigan Racing | +1.5427 |
| 17 | 20 | Conor Daly | USA | Ed Carpenter Racing | +1.5971 |
| 18 | 59 | Max Chilton | GBR | Carlin | +1.6005 |
| 19 | 22 | Simon Pagenaud | FRA | Team Penske | +1.6162 |
| 20 | 18 | Ed Jones | UAE | Dale Coyne Racing | +1.8041 |
| 21 | 60 | Jack Harvey | GBR | Meyer Shank Racing | +2.0365 |
| 22 | 45 | Santino Ferrucci | USA | Rahal Letterman Lanigan Racing | +2.0639 |
| 23 | 4 | Dalton Kellett | CAN | AJ Foyt Enterprises | +3.5303 |
| 24 | 3 | Scott McLaughlin | NZL | Team Penske | +3.8486 |
| 25 | 48 | Jimmie Johnson | USA | Chip Ganassi Racing | +5.4585 |
