James Hinchcliffe used his final flying lap to go fastest in the third IndyCar practice session at Barber.
The Canadian, whose Andretti team-mate Ryan Hunter-Reay topped both Friday sessions, became the first driver of the weekend to dip below the 1m08s barrier when he delivered a 1m07.9206s with just one minute left on the clock.
Up to that point the benchmark had been Sebastien Bourdais, whose fastest time had remained unbeaten for nearly half an hour before Hinchliffe improved on it by 0.1 seconds.
But there was little to separate any of the frontrunners: the top 18 drivers were covered by just one second.
Scott Dixon recovered from an early trip through the grass to go third-fastest ahead of Helio Castroneves, who caused the only red flag when his car stopped on the track at the session's halfway point.
His Penske team-mate Will Power also survived a scare on his way to fifth-fastest; the Australian escaping a lurid spin that almost deposited him into the wall.
It was a tough session for Tony Kanaan who finished the session down in 21st place, with the Ganassi team reporting an ongoing struggle to find an optimal set-up.
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Pos Driver Team/Engine Time Gap Laps
1. James Hinchcliffe Andretti/Honda 1m07.9206s 15
2. Sebastien Bourdais KV/Chevy 1m08.0290s +0.1084s 19
3. Scott Dixon Ganassi/Chevy 1m08.0916s +0.1710s 14
4. Helio Castroneves Penske/Chevy 1m08.1611s +0.2405s 21
5. Will Power Penske/Chevy 1m08.1670s +0.2464s 22
6. Ryan Hunter-Reay Andretti/Honda 1m08.1956s +0.2750s 14
7. Simon Pagenaud Schmidt/Honda 1m08.2083s +0.2877s 20
8. Josef Newgarden Fisher/Honda 1m08.2891s +0.3685s 17
9. Takuma Sato Foyt/Honda 1m08.3245s +0.4039s 23
10. Ryan Briscoe Ganassi/Chevy 1m08.3774s +0.4568s 16
11. Carlos Munoz Andretti/Honda 1m08.4454s +0.5248s 17
12. Juan Pablo Montoya Penske/Chevy 1m08.5097s +0.5891s 17
13. Justin Wilson Coyne/Honda 1m08.5359s +0.6153s 20
14. Charlie Kimball Ganassi/Chevy 1m08.6198s +0.6992s 19
15. Graham Rahal Rahal/Honda 1m08.6229s +0.7023s 20
16. Mikhail Aleshin Schmidt/Honda 1m08.6785s +0.7579s 17
17. Oriol Servia Rahal/Honda 1m08.7458s +0.8252s 18
18. Mike Conway Carpenter/Chevy 1m08.7848s +0.8642s 20
19. Marco Andretti Andretti/Honda 1m08.9432s +1.0226s 10
20. Sebastian Saavedra KV/Chevy 1m09.0011s +1.0805s 18
21. Tony Kanaan Ganassi/Chevy 1m09.0241s +1.1035s 13
22. Jack Hawksworth Herta/Honda 1m09.2564s +1.3358s 17
23. Carlos Huertas Coyne/Honda 1m09.2878s +1.3672s 19