Will Power was quickest in Friday practice as the IndyCar Series drivers got to grips with the Motegi road course for the first time.
With Helio Castroneves second and Ryan Briscoe fourth, only Newman/Haas' James Hinchcliffe prevented an all-Penske top three.
Hinchcliffe had been quickest going into the closing stages, before Castroneves grabbed the top spot with a 1m39.5965s. He then had a spin at the first corner, and while recovering his team-mate Power deposed him with a 1m39.4745s. The times are still some way off the 1m35s pole mark for the recent Formula Nippon event at the track.
The championship is using the venue's 2.983-mile road course for the first time this year, as the oval was damaged during March's earthquake in Japan. A further 6.2 magnitude quake struck the region late on Thursday afternoon, but did not cause any additional problems beyond being a little disconcerting for the visiting teams and drivers.
With IndyCar leaving Motegi after 2011, this weekend will be the only time the series races on the road course - and is also the last non-oval appearance for the current Dallara-Honda, with the Kentucky and Las Vegas speedways rounding out the calendar before the car is replaced by the new generation machine in 2012.
Behind the Penske trio and Hinchcliffe, Marco Andretti was fifth for Andretti Autosport, ahead of Sam Schmidt driver Alex Tagliani.
Championship leader Dario Franchitti (Ganassi) was quickest for some time before ending up seventh.
Guest driver Joao Paulo de Oliveira - a winner here in Formula Nippon last month - acclimatised to IndyCar very rapidly and made the most of his local knowledge to take eighth for Conquest Racing.
Sebastien Bourdais continued his recent strong form in ninth in the Dale Coyne car.
The two local heroes were next up - Takuma Sato completing the top 10 in the fastest of the KV entries, and returnee Hideki Mutoh going 11th for AFS/Sam Schmidt.
The session ran uninterrupted, with the only other incidents being quick spins for Tagliani and Giorgio Pantano (Dreyer & Reinbold), and a trip through the first corner gravel for Dale Coyne Racing's James Jakes. The British rookie was still an encouraging 13th.
Today's 75-minute practice was the only Friday track action. Tomorrow there will be two more one-hour practice sessions before qualifying.
Pos Driver Team Time Gap 1. Will Power Penske 1m39.4745s 2. Helio Castroneves Penske 1m39.5965s + 0.1220s 3. James Hinchcliffe Newman/Haas 1m39.8531s + 0.3786s 4. Ryan Briscoe Penske 1m40.1887s + 0.7142s 5. Marco Andretti Andretti 1m40.2584s + 0.7839s 6. Alex Tagliani Sam Schmidt 1m40.2649s + 0.7904s 7. Dario Franchitti Ganassi 1m40.3108s + 0.8363s 8. Joao Paulo de Oliveira Conquest 1m40.3299s + 0.8554s 9. Sebastien Bourdais Dale Coyne 1m40.3948s + 0.9203s 10. Takuma Sato KV 1m40.4435s + 0.9690s 11. Hideki Mutoh AFS/Sam Schmidt 1m40.5328s + 1.0583s 12. JR Hildebrand Panther 1m40.5435s + 1.0690s 13. James Jakes Dale Coyne 1m40.5580s + 1.0835s 14. Tony Kanaan KV 1m40.6600s + 1.1855s 15. Scott Dixon Ganassi 1m40.7175s + 1.2430s 16. Ryan Hunter-Reay Andretti 1m40.7389s + 1.2644s 17. Vitor Meira Foyt 1m40.7961s + 1.3216s 18. EJ Viso KV 1m40.8351s + 1.3606s 19. Oriol Servia Newman/Haas 1m40.8577s + 1.3832s 20. Charlie Kimball Ganassi 1m40.9505s + 1.4760s 21. Giorgio Pantano Dreyer & Reinbold 1m40.9659s + 1.4914s 22. Graham Rahal Ganassi 1m41.2056s + 1.7311s 23. Mike Conway Andretti 1m41.2987s + 1.8242s 24. Danica Patrick Andretti 1m41.4164s + 1.9419s 25. Simona de Silvestro HVM 1m41.4495s + 1.9750s 26. Ana Beatriz Dreyer & Reinbold 1m41.4711s + 1.9966s