Dale Coyne Racing's Sebastien Bourdais topped final practice ahead of qualifying for this weekend's Grand Prix of Portland at Portland International Raceway.
Bourdais, who topped the first practice session of the weekend, set a best time of a 57.4707s before closing the session by bringing out the red flag, heading Rahal Letterman Lanigan Racing's Graham Rahal by 0.0435s.
Championship contender Will Power set the third fastest time in the #12 Team Penske Chevrolet, 00801s adrift of Bourdais' fastest time. Alexander Rossi followed Power on the timesheets in fourth fastest while Takuma Sato completed the top five in the #30 machine.
Spencer Pigot was sixth fastest, 0.0031s adrift of Sato while Ryan Hunter-Reay set the seventh fastest time in the #28 Andretti Autosport Honda.
After setting the second fastest time of free practice two, Marco Andretti dropped to eighth on the timesheets in FP3, 0.2736s off the pace.
Reigning IndyCar champion Josef Newgarden was ninth fastest while rookie Zach Veach completed the top 10, continuing his form from prior sessions to place himself in a good position for the penultimate round of the 2018 season.
Championship leader Scott Dixon only managed 11th in practice three and was followed by Jordan King, Santino Ferrucci, Ed Jones and Carlos Munoz who completed the top 15.
Honda Indy Toronto's winner James Hinchcliffe rounded out the session as the slowest of the 25 drivers after only managing to complete three laps in the session.
