Ryan Briscoe got past fellow Australian and Penske teammate Will Power out of a caution pit stop on Sunday and held off the two-time defending Sonoma champion for his first IndyCar victory since 2010.
After Power led for most of the race, Briscoe slipped into position for his eighth career victory when Power got caught in traffic following a scary crash for Sebastien Bourdais and Josef Newgarden.
Both drivers apparently avoided injury when Bourdais lost control on cold tyres and slammed Newgarden into a protective barrier.
Power barely failed to win his third straight race in Sonoma after starting from pole. He still increased his overall points lead over second-place Ryan Hunter-Reay, who was left fuming after Alex Tagliani spun him out shortly after the restart.