Graham Rahal put the Rahal Letterman Lanigan Racing-Honda on top by 0.7sec in raceday warm-up, helped by running softer compound tires, but all eyes were on the main championship protagonists.
Rahal lapped the 2.385-mile course in 1min16.9608sec, 0.7033sec ahead of the surprising Ed Carpenter Racing-Chevrolet of Spencer Pigot.
In third, however, was Scott Dixon’s Chip Ganassi Racing-Honda, a few hundredths ahead of Penske-Chevrolet’s Castroneves and Newgarden, as the four-time champion looks to overturn the qualifying form that saw Penske lock out the front two rows. Dixon is four points behind polesitter Newgarden in the championship chase.
Alexander Rossi and Marco Andretti both ran reds, and were sixth and seventh fastest, with their Andretti Autosport-Honda teammates Takuma Sato and Ryan Hunter-Reay in eighth and 10th. RHR split the AJ Foyt Racing-Chevys of Carlos Munoz and COnor Daly.
Ahead of his final race for Chip Ganassi Racing, Max Chilton had a harmless spin in Turn 3, but rebounded to go 12th fastest, but teammate Charlie Kimball was less lucky, braking issues causing him to complete only two laps just before the checker fell.
IndyCar debutant Zachary Claman DeMelo was 13th for RLLR.
Sonoma, IndyCar warm-up
|13||13||Zachary Claman DeMelo||18||1'18.3122||1.3514||0.0375||109.638|