Reigning series champion Will Power's best lap of 1:17.4858 in the No. 1 Verizon Team Penske Chevrolet was good enough to top the three-hour, 30-minute-long Practice 1 of the GoPro Grand Prix of Sonoma weekend on Friday evening.
Joining the Australian in the 1:17's were Graham Rahal, Ryan Hunter-Reay, Scott Dixon, Marco Andretti and Simon Pagenaud, who completed the top-six behind Power's No. 1 Chevrolet-powered Penske entry.
Juan Pablo Montoya, who has led the points since the first checkered flag of the season at St. Petersburg, was 0.6043-seconds behind his Penske teammate Power, putting him down in ninth.
The three-and-a-half hour long session, being as long as it was, saw the temperature at Sonoma Raceway drop from 94 to 86 degrees in ambient temperature; the track dropped from 129 to 111 degrees during the long free practice session. The unusually-long session, being coined a 'marathon session', saw 984 total laps completed by the field.
Many drivers had trouble in the chicane section of the course throughout the session; no severe incidents took place at that area of the challenging Sonoma Raceway circuit, though.
The lone red flag of the session lasted a mere three minutes and 32 seconds and came out just after the green flag got the weekend underway. Oriol Servia stopped the No. 25 Andretti Autosport Honda at Turn 2 before turning around and heading back to pit lane backwards on the track. In Justin Wilson's car which displays tributes to the driver who passed away on Monday, Servia finished the day 25th quickest with a best lap time of 1:19.6981.