Colton Herta went fastest for Harding Steinbrenner Racing-Honda in second free practice for the IndyCar Grand Prix on the Indianapolis Motor Speedway road course.
Herta was 0.378 seconds clear of the field on the primary tyres and was also comfortably quickest on Firestone's alternate compound.
Ultimately, he was 0.2078sec faster than Chip Ganassi Racing's Felix Rosenqvist, and set a 68.0393sec lap, at an average speed of 129.049mph around the 2.439-mile course.
Rosenqvist was precisely 0.05 seconds faster than teammate Scott Dixon but the pair were separated by Spencer Pigot - shining again for Ed Carpenter Racing as he did in opening practice - and Sebastien Bourdais in the Dale Coyne Racing with Vasser-Sullivan Honda.
Dixon had a brief off-course excursion but held onto fifth ahead of Takuma Sato's Rahal Letterman Lanigan Racing and Ryan Hunter-Reay in the fastest of the Andretti Autosports.
Jack Harvey's Meyer Shank Racing with SPM was eighth fastest ahead of semi-teammate Arrow SPM driver Marcus Ericsson.
Ed Jones in the second ECR-Chevy was 10th despite causing a red flag in the opening 10 minutes when he ran out of fuel and needed a tow-in.
Santino Ferrucci slotted the second Coyne car ahead of Long Beach winner Alexander Rossi and the second RLLR car of Graham Rahal.
Josef Newgarden headed the Team Penskequartet, while Matheus Leist was 0.75 seconds clear of AJ Foyt Racing team-mate Tony Kanaan.
Carlin's Patricio O'Ward - newly announced as a Red Bull junior driver - did not complete a lap on the alternate compound tires and finished last.
|1||Colton Herta||Harding Racing||Dallara/Honda||1m08.0393s||-|
|2||Felix Rosenqvist||Chip Ganassi Racing||Dallara/Honda||1m08.2471s||0.2078s|
|3||Spencer Pigot||Ed Carpenter Racing||Dallara/Chevrolet||1m08.2663s||0.2270s|
|4||Sebastien Bourdais||Dale Coyne Racing||Dallara/Honda||1m08.2971s||0.2578s|
|5||Scott Dixon||Chip Ganassi Racing||Dallara/Honda||1m08.2971s||0.2578s|
|6||Takuma Sato||Rahal Letterman Lanigan||Dallara/Honda||1m08.4690s||0.4297s|
|7||Ryan Hunter-Reay||Andretti Autosport||Dallara/Honda||1m08.5077s||0.4684s|
|8||Jack Harvey||Meyer Shank Racing||Dallara/Honda||1m08.5118s||0.4725s|
|9||Marcus Ericsson||Schmidt Peterson Motorsports||Dallara/Honda||1m08.5225s||0.4832s|
|10||Ed Jones||Ed Carpenter Racing||Dallara/Chevrolet||1m08.5350s||0.4957s|
|11||Santino Ferrucci||Dale Coyne Racing||Dallara/Honda||1m08.5406s||0.5013s|
|12||Alexander Rossi||Andretti Autosport||Dallara/Honda||1m08.5905s||0.5512s|
|13||Graham Rahal||Rahal Letterman Lanigan||Dallara/Honda||1m08.6096s||0.5703s|
|14||Josef Newgarden||Team Penske||Dallara/Chevrolet||1m08.6226s||0.5833s|
|15||Simon Pagenaud||Team Penske||Dallara/Chevrolet||1m08.6610s||0.6217s|
|16||Will Power||Team Penske||Dallara/Chevrolet||1m08.6799s||0.6406s|
|17||James Hinchcliffe||Schmidt Peterson Motorsports||Dallara/Honda||1m08.7654s||0.7261s|
|18||Helio Castroneves||Team Penske||Dallara/Chevrolet||1m08.7855s||0.7462s|
|20||Marco Andretti||Andretti Herta||Dallara/Honda||1m08.7902s||0.7509s|
|21||Zach Veach||Andretti Autosport||Dallara/Honda||1m08.8472s||0.8079s|
|22||Matheus Leist||AJ Foyt Enterprises||Dallara/Chevrolet||1m08.8628s||0.8235s|
|23||Tony Kanaan||AJ Foyt Enterprises||Dallara/Chevrolet||1m09.6147s||1.5754s|