Marco Andretti topped the timing screens for a second time on Friday, after heading the second one-hour practice session on Friday ahead of this weekend's Milwaukee IndyFest race.

Andretti improved his time to 21.6811s (168.534mph) in the second hour-long stint, with his Andretti Autosport team mate Ryan Hunter-Reay just five hundreds of a second back. AJ Foyt Racing's Takuma Sato was third fastest ahead of a third member of the Andretti squad, EJ Viso.

There were two brief interruptions to team activity on the one-mile flat oval, both times for track inspections.

Qualifying takes place later at 4.15pm local time (10.15pm BST) and takes the usual IZOD IndyCar Series format for oval races of a two-lap averaged time trial rather than the three-round system used for road and street course events.

Practice 2 times

1. #25 Marco Andretti (C) 168.534mph 21.6811s after 45 laps
2. #1 Ryan Hunter-Reay (C) 168.145mph 21.7312s + 0.0501s after 50 laps
3. #14 Takuma Sato (H) 168.117mph 21.7349s + 0.0538s after 62 laps
4. #5 EJ Viso (C) 167.140mph 21.8619s + 0.1808s after 49 laps
5. #9 Scott Dixon (H) 166.650mph 21.9262s + 0.2451s after 57 laps
6. #3 Helio Castroneves (C) 166.423mph 21.9561s + 0.2750s after 50 laps
7. #19 Justin Wilson (H) 166.303mph 21.9720s + 0.2909s after 63 laps
8. #16 James Jakes (H) 166.032mph 22.0078s + 0.3267s after 57 laps
9. #98 Alex Tagliani (H) 166.007mph 22.0111s + 0.3300s after 47 laps
10. #7 Sebastien Bourdais (C) 165.303mph 22.1048s + 0.4237s after 38 laps
11. #10 Dario Franchitti (H) 164.924mph 22.1556s + 0.4745s after 57 laps
12. #27 James Hinchcliffe (C) 164.904mph 22.1583s + 0.4772s after 50 laps
13. #6 Sebastian Saavedra (C) 164.697mph 22.1862s + 0.5051s after 48 laps
14. #67 Josef Newgarden (H) 164.591mph 22.2005s + 0.5194s after 58 laps
15. #77 Simon Pagenaud (H) 164.242mph 22.2477s + 0.5666s after 44 laps
16. #4 Ryan Briscoe (C) 164.110mph 22.2656s + 0.5845s after 56 laps
17. #12 Will Power (C) 163.883mph 22.2964s + 0.6153s after 53 laps
18. #11 Tony Kanaan (C) 163.578mph 22.3380s + 0.6569s after 39 laps
19. #18 Ana Beatriz (H) 163.461mph 22.3539s + 0.6728s after 61 laps
20. #15 Graham Rahal (H) 163.421mph 22.3594s + 0.6783s after 52 laps
21. #55 Tristan Vautier (H) 162.890mph 22.4323s + 0.7512s after 53 laps
22. #78 Simona De Silvestro (C) 162.123mph 22.5384s + 0.8573s after 54 laps
23. #83 Charlie Kimball (H) 160.375mph 22.7841s + 1.1030s after 52 laps
24. #20 Ed Carpenter (C) 158.902mph 22.9953s + 1.3142s after 43 laps

Total Laps: 1238

Combined Friday practice times

1. #25 Marco Andretti (C) 168.534mph 21.6811s Practice 2 (80 laps)
2. #1 Ryan Hunter-Reay (C) 168.145mph 21.7312s Practice 2 (85 laps)
3. #14 Takuma Sato (H) 168.117mph 21.7349s Practice 2 (92 laps)
4. #5 EJ Viso (C) 167.140mph 21.8619s Practice 2 (86 laps)
5. #9 Scott Dixon (H) 166.650mph 21.9262s Practice 2 (93 laps)
6. #3 Helio Castroneves (C) 166.423mph 21.9561s Practice 2 (86 laps)
7. #19 Justin Wilson (H) 166.303mph 21.9720s Practice 2 (99 laps)
8. #67 Josef Newgarden (H) 166.086mph 22.0006s Practice 1 (109 laps)
9. #16 James Jakes (H) 166.032mph 22.0078s Practice 2 (105 laps)
10. #98 Alex Tagliani (H) 166.007mph 22.0111s Practice 2 (93 laps)
11. #55 Tristan Vautier (H) 165.637mph 22.0603s Practice 1 (109 laps)
12. #12 Will Power (C) 165.626mph 22.0618s Practice 1 (111 laps)
13. #7 Sebastien Bourdais (C) 165.303mph 22.1048s Practice 2 (91 laps)
14. #11 Tony Kanaan (C) 165.170mph 22.1226s Practice 1 (72 laps)
15. #10 Dario Franchitti (H) 164.924mph 22.1556s Practice 2 (79 laps)
16. #27 James Hinchcliffe (C) 164.904mph 22.1583s Practice 2 (67 laps)
17. #6 Sebastian Saavedra (C) 164.697mph 22.1862s Practice 2 (107 laps)
18. #78 Simona De Silvestro (C) 164.376mph 22.2295s Practice 1 (113 laps)
19. #18 Ana Beatriz (H) 164.242mph 22.2477s Practice 1 (134 laps)
20. #77 Simon Pagenaud (H) 164.242mph 22.2477s Practice 2 (99 laps)
21. #4 Ryan Briscoe (C) 164.110mph 22.2656s Practice 2 (112 laps)
22. #83 Charlie Kimball (H) 163.645mph 22.3288s Practice 1 (113 laps)
23. #15 Graham Rahal (H) 163.504mph 22.3481s Practice 1 (100 laps)
24. #20 Ed Carpenter (C) 161.845mph 22.5771s Practice 1 (86 laps)

Total Laps for Combined Sessions: 2321