The two-time IndyCar champion lapped the legendary Indianapolis Motor Speedway at 227.686mph, 0.9mph ahead of 2008 Indy 500 winner Scott Dixon.
That’s the way it remained until very late in the session when 1Conor Daly sprung into the 227s, laying down a 227.466mph lap in his Ed Carpenter Racing entry.
Behind Dixon was Long Beach winner Kyle Kirkwood, who was fourth fastest for Andretti Autosport ahead of double Indy 500 winner Takuma Sato for Chip Ganassi Racing.
With the second day of testing forecast to be blighted by showers, the track was very busy as teams plowed through their nine-set Firestone tyre allocation.
The pressure to get as much of Friday's work done on Thursday meant the drivers felt compelled to hit the track even though conditions were far from ideal, as strong headwinds along the front straight, tail winds on the back straight, and gusts of up to 30mph hit the circuit.
Source: Autosport