Penske had the two fastest laps of Friday's six-hour practice session for the Indianapolis 500, with Ryan Briscoe quickest on a time of 39.8263 seconds (225.981 mph).
He was followed by team-mate Helio Castroneves at 39.9223s (225.438 mph) while Will Power, driving the team's third entry, was clocked seventh-fastest of the 33 cars on the track.
Briscoe and Castroneves were slightly ahead of their rivals at Chip Ganassi Racing, which is fielding the winners of the last two Indianapolis 500s. Dario Franchitti and Scott Dixon were third and fourth.
When asked if he felt the Ganassi drivers were sandbagging in practice, Briscoe replied: "I hope not," recalling Dixon's return to the track to regain the pole from him last year.
"I'm feeling good, though," Briscoe said. "I think the car is running very solid. We've done some non-drafting laps, and the car's been fast. Tomorrow is another day, and everyone is going to be going for it. Hopefully there won't be any surprises and we can stay at the top."
Andretti Green Racing and Panther Racing also should be in the hunt when qualifying begins at noon local time on Saturday. Danica Patrick and Marco Andretti had the fifth- and sixth-fastest laps of the day, while Panther's Dan Wheldon was eighth.
"It's great to start up front, but it's a 500-mile race," Patrick said. "I remember in 2005 when Mr Wheldon won from the middle of the pack. Anything is possible."
Saturday's session is expected to be hampered by colder temperatures and wind, but forecasts do not predict rain. Rain surrounded the track on Friday but never caused lengthy delays.
"Tomorrow will be a whole other unique set of conditions for us, really," Dixon said. "The weather here in Indianapolis has been quite unpredictable, but we think we have a strong shot at the pole for tomorrow. The Penske cars have been pretty fast, though. Dario has been strong, as well, so we're optimistic about getting solidly into the race."
Three drivers were involved in costly crashes on Friday, the worst sustained by Scott Sharp. His Panther Racing Dallara spun suddenly in Turn 1, ending his day.
"It just snapped on me," Sharp said. "I'm not exactly sure what's up. I have to go back and figure all of that out with the Panther team. We've been struggling a little bit to gain more speed and didn't really need this to happen right now. We'll see what the plan is and find a way to rebound."
Ryan Hunter-Reay and Robert Doornbos spun and hit the wall earlier in the day, but both returned. Vision Racing repaired the light damage to Hunter-Reay's #21 car and got it back on track. Doornbos returned in his T car.
The surprise of the week so far - Alex Lloyd in the Ganassi/Sam Schmidt #99 car - could have a shot at making the top 11 on Saturday. His lap of 224.219 mph was the 10th best of the day.
"We're in the window where we're pretty happy," Lloyd said. "We're pleased with the speed of the car, and I think we can go a little bit quicker if we take off a little more downforce. Obviously, the aim is to try to get qualified tomorrow, and I think we've got a car that's capable of doing that."
The top 11 positions on the 33-car starting grid will be determined by Saturday's qualifying. Once 11 positions are filled, drivers will begin to bump one another out of the top 11.
Pos Driver Team Time Gap 1. Ryan Briscoe Penske 39.8263s 2. Helio Castroneves Penske 39.9223s + 0.0960s 3. Dario Franchitti Ganassi 40.0029s + 0.1766s 4. Scott Dixon Ganassi 40.0317s + 0.2054s 5. Danica Patrick Andretti Green 40.0436s + 0.2173s 6. Marco Andretti Andretti Green 40.0492s + 0.2229s 7. Will Power Penske 40.0733s + 0.2470s 8. Dan Wheldon Panther 40.1146s + 0.2883s 9. Hideki Mutoh Andretti Green 40.1388s + 0.3125s 10. Alex Lloyd Schmidt/Ganassi 40.1393s + 0.3130s 11. Graham Rahal Newman/Haas/Lanigan 40.1528s + 0.3265s 12. Tony Kanaan Andretti Green 40.1726s + 0.3463s 13. Robert Doornbos Newman/Haas/Lanigan 40.1867s + 0.3604s 14. Mario Moraes KV 40.2549s + 0.4286s 15. Vitor Meira Foyt 40.2573s + 0.4310s 16. Paul Tracy KV 40.2916s + 0.4653s 17. Raphael Matos Luczo Dragon 40.4203s + 0.5940s 18. Sarah Fisher Fisher 40.4596s + 0.6333s 19. John Andretti Petty/Dreyer & Reinbold 40.5262s + 0.6999s 20. Ed Carpenter Vision 40.5367s + 0.7104s 21. Davey Hamilton Dreyer & Reinbold 40.5440s + 0.7177s 22. Scott Sharp Panther 40.5882s + 0.7619s 23. Justin Wilson Coyne 40.5885s + 0.7622s 24. Alex Tagliani Conquest 40.6250s + 0.7987s 25. AJ Foyt IV Foyt 40.7525s + 0.9262s 26. EJ Viso HVM 40.7540s + 0.9277s 27. Ryan Hunter-Reay Vision 40.7949s + 0.9686s 28. Mike Conway Dreyer & Reinbold 40.8163s + 0.9900s 29. Nelson Philippe HVM 40.9376s + 1.1113s 30. Milka Duno Dreyer & Reinbold 40.9708s + 1.1445s 31. Stanton Barrett 3G 41.1506s + 1.3243s