Simona de Silvestro topped the final practice session ahead of qualifying for this weekend's IndyCar race at Barber Motorsports Park.
As a sign of what could be to come later in the day, all but two of the field posted times below the official track record held by Will Power, with de Silvestro's 1m07.4073s effort bettering Power's record by 1.4 seconds.
"I'm sure [leading practice] does a lot [for my confidence]," de Silvestro said.
"I think the car is pretty good this morning. We have to see how the track is going to change for a little bit later, but the car has been pretty quick.
"I felt like every session we made improvements. Yesterday we were alright too, but it's nice to have the lap time up there now."
Simon Pagenaud came closest to matching de Silvestro with a lap just 0.09s slower than that posted by the Swiss driver, with mid-session leader Scott Dixon finishing up third fastest ahead of reigning champion Ryan Hunter-Reay, Dario Franchitti and JR Hildebrand.
Single-seater returnee AJ Allmendinger was quickest of the Penske drivers in seventh, leaving his full-time stable-mates Power and Helio Castroneves in 10th and 12th respectively.
Rookie Tristan Vautier also continued his strong start to the weekend, finishing the morning eighth fastest behind Allmendinger.
The session was interrupted by one brief stoppage when Sebastien Bourdais spun and stalled in the middle of the track, although the Frenchman's car was undamaged and he was able to continue running after the restart.
Pos Driver Team Time Gap Laps 1. Simona de Silvestro KV Dallara-Chevy 1m07.4073s 13 2. Simon Pagenaud Schmidt Dallara-Honda 1m07.4986s + 0.0913 14 3. Scott Dixon Ganassi Dallara-Honda 1m07.5343s + 0.1270 12 4. Ryan Hunter-Reay Andretti Dallara-Chevy 1m07.5970s + 0.1897 12 5. Dario Franchitti Ganassi Dallara-Honda 1m07.7162s + 0.3089 10 6. JR Hildebrand Panther Dallara-Chevy 1m07.7491s + 0.3418 11 7. AJ Allmendinger Penske Dallara-Chevy 1m07.7526s + 0.3453 14 8. Tristan Vautier Schmidt Dallara-Honda 1m07.8433s + 0.4360 13 9. Justin Wilson Coyne Dallara-Honda 1m07.8497s + 0.4424 16 10. Will Power Penske Dallara-Chevy 1m07.8529s + 0.4456 17 11. James Hinchcliffe Andretti Dallara-Chevy 1m07.8714s + 0.4641 14 12. Helio Castroneves Penske Dallara-Chevy 1m07.8942s + 0.4869 8 13. Alex Tagliani Herta Dallara-Honda 1m07.9645s + 0.5572 12 14. EJ Viso Andretti Dallara-Chevy 1m07.9889s + 0.5816 11 15. Sebastien Bourdais Dragon Dallara-Chevy 1m08.0075s + 0.6002 13 16. James Jakes Rahal Dallara-Honda 1m08.0254s + 0.6181 13 17. Tony Kanaan KV Dallara-Chevy 1m08.0770s + 0.6697 13 18. Graham Rahal Rahal Dallara-Honda 1m08.1028s + 0.6955 14 19. Charlie Kimball Ganassi Dallara-Honda 1m08.1033s + 0.6960 7 20. Oriol Servia Panther/DRR Dallara-Chevy 1m08.1302s + 0.7229 16 21. Josef Newgarden Fisher Dallara-Honda 1m08.1415s + 0.7342 10 22. Sebastian Saavedra Dragon Dallara-Chevy 1m08.1731s + 0.7658 16 23. Marco Andretti Andretti Dallara-Chevy 1m08.2191s + 0.8118 11 24. Takuma Sato Foyt Dallara-Honda 1m08.3161s + 0.9088 17 25. Ed Carpenter Carpenter Dallara-Chevy 1m09.2225s + 1.8152 18 26. Ana Beatriz Coyne Dallara-Honda 1m09.9290s + 2.5217 18