Driving the No. 9 Target Chip Ganassi Racing car, Dixon set a 1m09.5969 to top the charts.
Ryan Briscoe was second quickest in the No. 8 NTT Data car for Ganassi Racing (1m09.6558)
Frenchman Simon Pagenaud was third (1m09.7544) in the No. 77 Schmidt Peterson Hamilton Motorsports car and posted the most laps (57).
Three-time Indianapolis 500 champion Helio Castroneves (1m10.0209) was fourth in the No. 3 Verizon Team Penske car, and Ryan Hunter-Reay (1m10.0237) was fifth in the No. 28 DHL car for Andretti Autosport.
Originally laid out for the Formula 1 race, the road course underwent a $5 million reconfiguration and infrastructure upgrade that includes new viewing mounds for spectators looking over the oval Turn 2.