Helio Castroneves and Will Power put Team Penske 1-2 in the afternoon session at Phoenix International Raceway, with Ed Carpenter Racing’s Josef Newgarden and Juan Montoya making it a Chevrolet 1-2-3-4.
A late surge from Graham Rahal’s Rahal Letterman Lanigan Racing entry gave Honda fifth, but he was some 2.5mph shy of Castroneves’ benchmark pace, which was a 187.850mph / 19.5858sec lap.
Marco Andretti headed the Andretti Autosport trio in seventh, narrowly eclipsing reigning champion Scott Dixon, who led the Chip Ganassi Racing quartet in eighth.
Indy Lights graduate Max Chilton, whose first oval test in an IndyCar came at Auto Club Speedway two weeks ago, was 14th fastest in the #8 Ganassi car.
Luca Filippi, who has briefly tested on an oval (Iowa) but has only raced road and street courses in IndyCar up to now, was only 20th fastest out of the 21 cars, but was just 0.01 slower than Dale Coyne Racing teammate Conor Daly.
Gabby Chaves, who is without a ride for 2016 but is substituting for Mikhail Aleshin (currently trying to renew his work visa) in the Schmidt Peterson Motorsports #7, was a fine 11th fastest.
The evening session at PIR runs from 5pm - 8pm local time.