The three-time Supercars champion delivered a 1min10.8755sec lap of the 2.238-mile course, an average speed of 113.675mph, which put him 0.1469sec clear of Andretti Autosport’s 2019 Laguna Seca pole-winner Colton Herta.
Third fastest was championship leader Alex Palou, the only Chip Ganassi Racing driver in the Top 10, with Simon Pagenaud and Will Power fourth and fifth for Penske.
Felix Rosenqvist was the quicker of the two Arrow McLaren SP, after title challenger Pato O’Ward flat spotted one of his tires, while Alexander Rossi and Ryan Hunter-Reay ensured there were three Andretti cars in the Top 10.
After the green flag waved following a shunt for Rinus VeeKay, there were just four minutes remaining, and all cars headed out for a trial run of the softer Firestone ‘reds’.
The Turn 4 shunt completed a scrappy session for the Ed Carpenter Racing driver who had early in the session ventured through the Turn 2 gravel after roasting his left-front tire under braking.
He wasn’t the only driver to cause a red flag, as Dalton Kellett also backed his car off the track at Turn 4.
Takuma Sato was lucky not to bring out the reds after a wild excursion through the sand and gravel exiting the uphill Turn 5, but his Rahal Letterman Lanigan car demolished a couple of advertising hoardings as it went broadside, but managed to avoid the tyres and the two-time Indy 500 winner was able to regain the track without outside assistance.
Callum Ilott, set to make his second IndyCar start tomorrow, did an impressive job to land 19th fastest time, the Juncos-Hollinger driver just 1.2sec from top spot.
Qualifying starts at 2.05pm local (Pacific) time.