Martin Plowman was a surprise pace-setter in the second IndyCar practice session at Sears Point on Saturday.
The AFS/Sam Schmidt Motorsports driver was one of several to capitalise on the extra grip from the softer-compound red slick tyres on offer to move up the order, and the Brit finished the session with a best lap of 1m19.0350s.
Friday pace-setters Dario Franchitti and Will Power were just behind him for the Ganassi and Penske teams respectively, both title contenders having opted to stay on the harder rubber.
Behind them, JR Hildebrand (Panther Racing) and James Jakes (Dale Coyne Racing) used the reds to go fourth and fifth-quickest respectively.
A late yellow flag triggered by a spinning Ana Beatriz potentially derailed a few drivers' hopes of improving their times.
The track returned to green with a couple of minutes remaining, but there was not enough time for any significant changes to the order.
Pos Driver Team Time Gap
1. Martin Plowman AFS/Sam Shmidt 1m19.035s
2. Dario Franchitti Ganassi 1m19.039s + 0.004s
3. Will Power Penske 1m19.040s + 0.005s
4. JR Hildebrand Panther 1m19.124s + 0.093s
5. James Jakes Dayle Coyne 1m19.137s + 0.102s
6. Scott Dixon Ganassi 1m19.143s + 0.108s
7. Ryan Briscoe Penske 1m19.256s + 0.221s
8. Sebastian Saavedra Conquest 1m19.361s + 0.326s
9. Mike Conway Andretti 1m19.455s + 0.420s
10. Helio Castroneves Penske 1m19.458s + 0.423s
11. Ho-Pin Tung Sam Schmidt Dragon 1m19.704s + 0.669s
12. Graham Rahal Ganassi 1m19.752s + 0.717s
13. Giorgio Pantano Dreyer & Reinbold 1m19.799s + 0.764s
14. Sebastien Bourdais Dale Coyne 1m19.838s + 0.803s
15. Ernesto Viso KV 1m19.885s + 0.850s
16. Danica Patrick Andretti 1m19.891s + 0.856s
17. Takuma Sato KV 1m19.900s + 0.865s
18. Charlie Kimball Ganassi 1m19.983s + 0.948s
19. James Hinchcliffe Newman/Haas 1m19.987s + 0.952s
20. Ryan Hunter-Reay Andretti 1m20.014s + 0.979s
21. Oriol Servia Newman/Haas 1m20.016s + 0.981s
22. Marco Andretti Andretti 1m20.025s + 0.990s
23. Tony Kanaan KV 1m20.060s + 1.025s
24. Simon Pagenaud HVM 1m20.116s + 1.081s
25. Ana Beatriz Dreyer & Reinbold 1m20.141s + 1.106s
26. Alex Tagliani Sam Schmidt 1m20.522s + 1.487s
27. Vitor Meira Foyt 1m20.748s + 2.713s
28. Ed Carpenter Sarah Fisher 1m20.872s + 1.837s