Juan Pablo Montoya at Auto Club Speedway

After running on the one-mile Phoenix International Raceway on Dec. 10, Juan Pablo Montoya stretched his legs Dec. 12 on the two-mile Auto Club Speedway oval in Fontana, Calif.

The test sessions are part of Montoya's acclimation to the Chevrolet-powered No. 2 Team Penske car in preparing for the 18-race IndyCar Series season. On Dec. 16, he'll drive on the 2.385-mile, 12-turn Sonoma Raceway road course, where he won his initial NASCAR Sprint Cup race in 2007.

"These were two important tests for me, especially the Phoenix test," Montoya said. "The short ovals are going to be my biggest challenge because you have to run flat out. That wasn't the case when I was in the series in 1999 and 2000. The speed you carry through the corners is unbelievable."

In his NASCAR Cup Series career, Montoya made a combined 25 starts at both Phoenix and Auto Club Speedway.

"The way you drive these two tracks is completely different from NASCAR to IndyCar," Montoya added. "We're running about 6 seconds a lap faster than in NASCAR."

Last month, the 2000 Indianapolis 500 winner and 1999 CART champion tested on the 1.65-mile Sebring International Raceway short course. Helio Castroneves, the 2013 IZOD IndyCar Series championship runner-up and three-time Indy 500 champion, has taken some early laps to shake down the car at each stop.

"I appreciate Helio making time to come out. He was a huge help," Montoya said. "I learned a long time ago that it's easier on you to work on the car and make it do what you want. Before I would just drive it, but today we had a great plan and took small steps to get where we needed to be."

Following a break for the holidays, Montoya will join Castroneves and Will Power for a manufacturer test in mid-January at Sebring. An Open Test is scheduled for March 16-17 at Barber Motorsports Park, and the season-opening Firestone Grand Prix of St. Petersburg is March 28-30.

"I told (team owner) Roger (Penske) that it's easy to see why he has so much success in this series," Montoya said. "These cars are so fast. The people on these teams are very talented. I'm excited about this chapter of my career."