Herta lapped the 1.8-mile, 14-turn street circuit in his Honda-powered machine in 1m00.1331s, recording the fastest time of the weekend thus far.
This was a regular format session after yesterday’s trial of quickfire multiple split-format sessions, with all cars running throughout the 45 minutes this time.
Kyle Kirkwood set the early pace for Andretti Global with a 1m00.6821s, 0.0651s ahead of the Penske-run machines of Scott McLaughlin and Will Power.
Power, who is suffering from pollen allergies this weekend, then took P1 with 1m00.4101s.
Rinus VeeKay leapt to second place after 15 minutes had elapsed in his Ed Carpenter Racing entry to make it a Chevrolet-powered 1-2, two tenths off Power’s pace.
Newgarden produced 1m00.3872s with a third of the session to go to set the fastest time, 0.05s off Friday’s pacesetter Felix Rosenqvist for Meyer Shank Racing.
Herta then beat that with 1m00.1331s, setting the fastest time of the weekend so far by a quarter of a second. “It was good to feel the car and get set for qualifying,” said Herta.
Earlier, Herta had locked up taken a trip down the Turn 4 escape road early on but spun his car around and drove to the pits where the team went to work on an alternator problem. Once fixed, he bolted on fresh rubber and unleashed the fastest lap.
Behind Power in third, Pato O’Ward took fourth for Arrow McLaren with 1m00.5789s, four tenths off the pace, ahead of Romain Grosjean (on his debut for Juncos Hollinger Racing), VeeKay, Kirkwood, McLaughlin and the Chip Ganassi Racing cars of Scott Dixon and Marcus Armstrong. Rosenqvist slipped to 11th.
Kirkwood slapped the wall at Turn 2, damaging the right-rear corner of his car and putting him out of the session. He reported: “It’s just the nature of street course racing, I had my left-side tires ready but not my rights. As soon as I got to the first left-hander I tapped the wall at 120mph.
“We were fast out of the gate, so I set that time on old tires with a flatspot, so we should be good for qualifying.”
Reigning champion Alex Palou, this year sporting the colors of DHL, was only 20th fastest for CGR. McLaren’s supersub Callum Ilott was 15th, in for the injured David Malukas, while team-mate Alexander Rossi suffered a grassy off at the final turn on his way to 12th.
Agustin Canapino glanced the wall at the exit of the final corner in his JHR machine.
Rahal Letterman Lanigan Racing’s Graham Rahal reported brake issues, while his team-mate Christian Lundgaard came into the pits with his right-rear corner on fire.
Santino Ferrucci didn’t turn a lap due to an unspecified technical issue with his AJ Foyt Racing car.
| Pos | Nº | Driver | Car / Engine | Time | Gap | Laps |
| 1 | 26 | Colton Herta | Dallara/Honda | 1'00.1331 | 22 | |
| 2 | 2 | Josef Newgarden | Dallara/Chevrolet | 1'00.3872 | 0.2541 | 24 |
| 3 | 12 | Will Power | Dallara/Chevrolet | 1'00.4101 | 0.2770 | 25 |
| 4 | 5 | Patricio O'Ward | Dallara/Chevrolet | 1'00.5789 | 0.4458 | 32 |
| 5 | 77 | Romain Grosjean | Dallara/Chevrolet | 1'00.6033 | 0.4702 | 23 |
| 6 | 21 | R.van Kalmthout | Dallara/Chevrolet | 1'00.6201 | 0.4870 | 26 |
| 7 | 27 | Kyle Kirkwood | Dallara/Honda | 1'00.6821 | 0.5490 | 10 |
| 8 | 3 | Scott McLaughlin | Dallara/Chevrolet | 1'00.6900 | 0.5569 | 26 |
| 9 | 9 | Scott Dixon | Dallara/Honda | 1'00.7032 | 0.5701 | 22 |
| 10 | 11 | Marcus Armstrong | Dallara/Honda | 1'00.7346 | 0.6015 | 25 |
| 11 | 60 | Felix Rosenqvist | Dallara/Honda | 1'00.7580 | 0.6249 | 21 |
| 12 | 7 | Alexander Rossi | Dallara/Chevrolet | 1'00.7962 | 0.6631 | 20 |
| 13 | 45 | C.Lundgaard | Dallara/Honda | 1'00.8570 | 0.7239 | 21 |
| 14 | 28 | Marcus Ericsson | Dallara/Honda | 1'00.9078 | 0.7747 | 24 |
| 15 | 6 | Callum Ilott | Dallara/Chevrolet | 1'00.9220 | 0.7889 | 20 |
| 16 | 8 | Linus Lundqvist | Dallara/Honda | 1'00.9298 | 0.7967 | 27 |
| 17 | 15 | Graham Rahal | Dallara/Honda | 1'00.9898 | 0.8567 | 23 |
| 18 | 66 | Tom Blomqvist | Dallara/Honda | 1'01.0366 | 0.9035 | 23 |
| 19 | 78 | Agustín Canapino | Dallara/Chevrolet | 1'01.0417 | 0.9086 | 23 |
| 20 | 10 | Alex Palou | Dallara/Honda | 1'01.1011 | 0.9680 | 24 |
| 21 | 41 | Sting Ray Robb | Dallara/Chevrolet | 1'01.1040 | 0.9709 | 26 |
| 22 | 20 | C.Rasmussen | Dallara/Chevrolet | 1'01.1089 | 0.9758 | 25 |
| 23 | 18 | Jack Harvey | Dallara/Honda | 1'01.1704 | 1.0373 | 21 |
| 24 | 4 | Kyffin Simpson | Dallara/Honda | 1'01.2990 | 1.1659 | 28 |
| 25 | 30 | P.Fittipaldi | Dallara/Honda | 1'01.7242 | 1.5911 | 24 |
| 26 | 51 | Colin Braun | Dallara/Honda | 1'02.3571 | 2.2240 | 24 |
| 27 | 14 | Santino Ferrucci | Dallara/Chevrolet | - | - | 24 |
