Alex Palou topped the opening test session at The Thermal Club ahead of Christian Lundgaard and Marcus Armstrong.
The track proved to be tricky for some drivers who ran wide at Turn 3 over the two hours.
Arrow McLaren SP’s Alexander Rossi and Pato O’Ward set the fourth and fifth-quickest times in a critical session ahead of the $1 Million Challenge.
The opening two-hour test session at The Thermal Club got underway, and a flurry of cars left the pit lane to gather track time.
Dale Coyne Racing’s Colin Braun set the first time of the session at 1:49.2528 before a brief lull in the opening stages.
Reigning champion Palou usurped the American 15 minutes into the session, setting a 1:39.5149.
Scott Dixon improved to second place for Chip Ganassi Racing despite bouncing over the kerb at Turn 16.
Half an hour into the session, Palou had the quickest time ahead of Dixon, with Lundgaard in third for Rahal Letterman Lanigan.
The RLL driver quickly improved to second place with a 1:39.6974 as the track continued to gather grip.
Former Formula 1 driver Marcus Ericsson ran wide but avoided the wall and rejoined the circuit; the Swede sat 12th of the 12 cars that set a time.
The driver of the number 28 car recovered from his earlier mistake to take fifth place, just ahead of his Andretti teammate Kyle Kirkwood.
Two of Arrow McLaren SP’s drivers, O’Ward and Callum Ilott, broke into the top five, going fourth and fifth fastest with an hour and 15 minutes remaining.
Their teammate Rossi went quicker than both, slotting into P4 with a 1:39.9375.
Turn 16 continued to be an issue as Australian Will Power skipped over the kerb on consecutive laps and sat down in 13th place.
Halfway through the session, Palou remained at the top of the timesheets ahead of Lundgaard and Armstrong, just two-tenths of a second separating the top three.
Multiple drivers, including Rinus Veekay and Graham Rahal, ran off the track at Turn 3; both continued after driving over the dusty runoff area.
The reigning Indy 500 champion, Josef Newgarden, suffered a quiet session for Team Penske, sitting in 20th place with his best time of 1:41.2265.
The American improved to 17th place in the number two car towards the end of the first test session at The Thermal Club.
O’Ward improved to fourth place with a 1:39.9124 before Rossi went quicker than his Mexican teammate.
The left front brake on Ercisson’s Andretti caught fire. The Swede slowed down to try to cool the brakes before the fire put itself out.
The 33-year-old soon pitted after driving a few laps at a slower speed, with just over 10 minutes remaining to repair the damaged brake disc.
Palou remained the quickest driver after setting 24 laps. Kyffin Simpson, for Chip Ganassi Racing, set the most laps of any driver in the session with 32.
