Eight teams tested at the 12-turn, 2.385-mile road course, including Sarah Fisher Hartman Racing with full-season driver Josef Newgarden and Lucas Luhr getting his initial seat time in an IZOD IndyCar Series car. Luhr, a five-time American Le Mans Series champion, has been confirmed to race in Sonoma in the No. 97 Honda-powered car.
Also seeing his first track time was 2012 Japanese Formula 3 champion Ryo Hirakawa in the No. 18 Dale Coyne Racing car. Hirakawa has been competing in the Super Formula (formerly Formula Nippon) series this season. Full-season driver Justin Wilson is driving the No. 19 car.
Also on the track were 2006 race winner Marco Andretti, James Hinchcliffe, Ryan Hunter-Reay and E.J. Viso (Andretti Autosport), Sebastien Bourdais and Sebastian Saavedra (Dragon Racing), Ed Carpenter (Ed Carpenter Racing), and James Jakes and Graham Rahal (Rahal Letterman Lanigan Racing).
Briscoe is the defending race winner at Sonoma and has finished in the top five each of the past five visits to Sonoma. He started on the front row last year next to then-Team Penske teammate Will Power, who has won the past three poles at the track.