Sato lapped the 2.5-mile Indianapolis Motor Speedway oval in 38.3382s, a speed of 234.753mph, in his Honda-powered Chip Ganassi Racing car, ahead of Marco Andretti (Andretti Autosport) and Rinus VeeKay (Ed Carpenter Racing).
Sato also topped the four-lap average speeds – which is how qualifying is decided – at 233.413mph set in the closing minutes of the session, ahead of CGR team-mate Marcus Ericsson and Team Penske’s Josef Newgarden.
Fast Friday means the BorgWarner turbos common to the Honda and Chevrolet engines were wound up from 1.3-bar boost to 1.5-bar, a level at which they will remain until the end of qualifying on Sunday evening. It meant a power boost of up to 100bhp over the previous running.
Weather conditions were bright and sunny, but a strong breeze pushed the cars hard into Turn 3 at over 240mph, although that meant a headwind towards Turn 1.
Kyle Kirkwood set the bar for Andretti Autosport with 232.649mph, going on to set a four-lap average of 231.739mph.
Pato O’Ward took over at the top for Arrow McLaren at 232.710mph but had to bail out on his qualifying run after a moment at Turn 3, after hitting over 243mph on the backstretch. Conor Daly just topped that with 232.723mph for Ed Carpenter Racing.
Sato then stole the show with a lap of 234.753mph before almost brushing the wall at Turn 2 and abandoning his qualifying …