Dani Pedrosa edged team-mate Marc Marquez to lead a Honda one-two in the opening MotoGP practice session at Sepang.
Yamaha's Jorge Lorenzo was third, albeit six tenths of a second down on Pedrosa, while Gresini's Alvaro Bautista beat Valentino Rossi to fourth late on.
Tech 3's Cal Crutchlow was fifth fastest, but more than one second off the ultimate pace.
Pedrosa and Marquez had started the weekend in race direction, with Marquez given one penalty point following his clash with Pedrosa in the Aragon Grand Prix.
That decision means the rookie championship leader is potentially just one infraction away from being forced to start from the back of the grid.
He showed little sign of tempering his natural aggression however, pulling off a typically ballsy move on Nicky Hayden during the 40-minute session.
Marquez was unable to do anything about Pedrosa however, with the older Spaniard - who won at Sepang last year - hitting the front with half an hour to run with a 2m01.229s that would prove unbeaten for the remainder.
Lorenzo, who had been top until Pedrosa's surge, had to settle for third.
Rossi had also enjoyed a spell at the top early on, but was shuffled down the order by his factory rivals and then lost fourth to Bautista in the final minutes.
Stefan Bradl beat Ducati's Nicky Hayden to seventh, with Bradley Smith and Andrea Dovizioso rounding out the top 10 ahead of Colin Edwards, who finished top of the CRT pile.
Dovizioso pulled off an excellent save at Turn 12 in the final minute of what was otherwise an incident-free session.
Pos Rider Team/Bike Time Gap Laps 1. Dani Pedrosa Honda 2m01.229s 17 2. Marc Marquez Honda 2m01.596s +0.367s 18 3. Jorge Lorenzo Yamaha 2m01.623s +0.394s 15 4. Alvaro Bautista Gresini Honda 2m01.877s +0.648s 15 5. Valentino Rossi Yamaha 2m02.039s +0.810s 17 6. Cal Crutchlow Tech 3 Yamaha 2m02.370s +1.141s 18 7. Stefan Bradl LCR Honda 2m02.421s +1.192s 17 8. Nicky Hayden Ducati 2m02.632s +1.403s 17 9. Bradley Smith Tech 3 Yamaha 2m02.725s +1.496s 18 10. Andrea Dovizioso Ducati 2m03.039s +1.810s 15 11. Colin Edwards Forward FTR-Kawasaki 2m03.574s +2.345s 14 12. Andrea Iannone Pramac Ducati 2m03.596s +2.367s 16 13. Aleix Espargaro Aspar Aprilia 2m03.773s +2.544s 12 14. Hiroshi Aoyama Avintia FTR-Kawasaki 2m04.273s +3.044s 17 15. Hector Barbera Avintia FTR-Kawasaki 2m04.425s +3.196s 12 16. Claudio Corti Forward FTR-Kawasaki 2m04.703s +3.474s 15 17. Yonny Hernandez Pramac Ducati 2m04.785s +3.556s 16 18. Randy de Puniet Aspar Aprilia 2m04.902s +3.673s 14 19. Michael Laverty PBM Aprilia 2m05.319s +4.090s 14 20. Danilo Petrucci Ioda-Suter-BMW 2m05.638s +4.409s 16 21. Luca Scassa Cardion Aprilia 2m06.355s +5.126s 16 22. Bryan Staring Gresini FTR-Honda 2m06.693s +5.464s 17 23. Damian Cudlin PBM-Aprilia 2m07.642s +6.413s 15 24. Lukas Pesek Ioda-Suter-BMW 2m08.023s +6.794s 13