Jorge Lorenzo overcame the challenge of Marc Marquez to stamp his authority on day one of the Indianapolis MotoGP.
Lorenzo had been quickest by just 0.093s from Marquez this morning and the Repsol Honda star put up even stiffer opposition in the afternoon - leaving the pair exactly tied for the top lap time in the closing stages of FP2 .
But the Movistar Yamaha rider had a little more to give and edged 0.003s clear of the reigning champion, undefeated in America since joining MotoGP in 2013, on his very final lap.
While Lorenzo and Marquez were constant P1 contenders, world championship leader Valentino Rossi spent most of the session at the lower end of the top ten – dropping as far back as 14th.
A pit stop to fit a medium rear tyre - most riders used the hard compound front and rear in the hotter afternoon conditions - then moved Rossi into tenth, 0.672s from team-mate Lorenzo.
Rossi starts the second half of the MotoGP season with a 13-point lead over Lorenzo and will need to defend his top ten place in Saturday's FP3, to ensure direct passage to Qualifying 2.
Ducati enjoyed a return to front-running contention on Friday with Andrea Dovizioso third fastest in both sessions (+0.295s), and team-mate Andrea Iannone just 0.011s slower. Ducati (like Suzuki, Aprilia and the Open class riders) do not have access to the hard rear tyre, likely to be picked by the factory Honda and Yamahas for the race.
Cal Crutchlow was the top satellite rider in fifth for LCR Honda (+0.326s), with Tech 3 Yamaha's Pol Espargaro holding sixth (+0.502s) despite a massive highside at the end of the session. Espargaro signed a new Yamaha contract earlier today.
Dani Pedrosa (Repsol Honda), Scott Redding (Marc VDS Honda) and Bradley Smith (Tech 3 Yamaha) separated Espargaro from Rossi.
Avintia Ducati's Hector Barbera was the top Open rider in 14th, between the underpowered Suzukis of Maverick Vinales and Aleix Espargaro, with home star Nicky Hayden 16th on the Aspar Honda.
Forward Racing are missing this weekend's event due to financial difficulties following the arrest of team boss Giovani Cuzari, with former rider Stefan Bradl joining Aprilia for the remainder of this season.
The German impressed by being as high as 16th during FP2 and outpacing team-mate Alvaro Bautista by 0.4s.
Toni Elias, replacing the injured Karel Abraham on the AB Motoracing Open Honda, was 23rd and last but a respectable one-second from Bautista.
1. Jorge Lorenzo
2. Marc Marquez
3. Andrea Dovizioso
4. Andrea Iannone
5. Cal Crutchlow
6. Pol Espargaro
7. Dani Pedrosa
8. Scott Redding
9. Bradley Smith
10. Valentino Rossi
11. Danilo Petrucci
12. Yonny Hernandez
13. Maverick Viñales
14. Hector Barbera
15. Aleix Espargaro
16. Nicky Hayden
17. Mike Di Meglio
18. Jack Miller
19. Eugene Laverty
20. Stefan Bradl
21. Alex De Angelis
22. Alvaro Bautista
23. Toni Elias