INDIANAPOLIS – The importance of track time was plainly evident on the opening day of practice for the 100th Running of the Indianapolis 500 presented by PennGrade Motor Oil.

All 33 entered cars saw time on the 2.5-mile Indianapolis Motor Speedway oval, totaling 1,972 laps. The 33 cars on track is the most for an Indy 500 opening day since 2010.

CLICK HERE: Rookie/refresher practice results; Practice 1 results

Andretti Autosport led the way with its five drivers all finishing in the top six. Marco Andretti sat on top of the leaderboard with a lap of 228.978 mph in the No. 27 Snapple Honda.

“It was a definitely a good start for the team,” said Andretti, the 11th-year Verizon IndyCar Series driver who has finished in the top four at the Indy 500 five times but has yet to win the race. “I think our team in particular looks pretty stout because we looked at the weather and moved things forward on the test plan from later in the week.

“I think we’re really going to see how things will shake out in the next few days. I know how this month goes. It’s definitely a roller coaster, so we’re prepared for that, but it’s a good opening day.”

Andretti was followed by teammates Carlos Munoz in the No. 26 Andretti Autosport Honda (228.945), Ryan Hunter-Reay in the No. 28 DHL Honda (228.033) and rookie Alexander Rossi in the No. 98 Castrol Edge/Curb Honda (226.865). Townsend Bell, driving the No. 29 Honda, was sixth at 226.724 mph.

Rossi was among the five Indy 500 rookies who participated in the two-hour rookie/veteran refresher session that opened the day. The 24-year-old Californian enjoyed the extra track time before the oval opened to all competitors for the final four hours.

“It felt fast,” the ex-Formula One driver said. “It was definitely eye-opening in terms of not having any kind of prior comparison to a place like this. I was glad we got through (rookie orientation) without any issues, and this afternoon we got to work and it was a very good day for the team in general.”

Scott Dixon, the reigning Verizon IndyCar Series champion and 2008 Indianapolis 500 winner, was fifth on the chart and fastest of the Chevrolet drivers with a lap of 226.835 mph in the No. 9 Target Chip Ganassi Racing entry.

“We tried a number of things today with the car, but no one is going for big numbers this early out there,” Dixon said. “No issues overall and looking forward to getting closer to qualifying trim tomorrow.”

Defending Indianapolis 500 champion Juan Pablo Montoya was 13th fastest at 224.613 mph in the No. 2 Verizon Team Penske Chevrolet. The entire day ran incident-free.

Rahal Letterman Lanigan Racing rookie Spencer Pigot was the busiest driver in both of today’s sessions, turning a total of 161 laps in the No. 16 RLL/Mi-Jack/Manitowac Honda.

“It was a lot of fun out there,” Pigot, 22, said. “I have always been looking forward to the day that I got to drive an Indy car around this track, so it was a great experience. We gradually built speed through the day and got through (rookie orientation) and did a lot of laps.

“The car feels good in traffic,” the Florida native added. “There is a lot more for me to learn and get used to as the days go on, but I think it was a good first day.”

Practice for the 100th Running of the Indianapolis 500 continues Tuesday through Friday, from noon to 6 p.m. ET each day. Qualifying to set the 33-car field will be held Saturday and Sunday. The May 29 race airs at 11 a.m. ET on ABC and the Advance Auto Parts INDYCAR Radio Network.

Rookies and refreshers get track time first

Five Indianapolis 500 rookies and five veteran part-time drivers took part in the two-hour rookie orientation and veteran refresher session.

Rossi, Pigot, Matt Brabham (No. 61 PIRTEK Team Murray Chevrolet), Max Chilton (No. 8 Gallagher Chip Ganassi Racing Teams Chevrolet) and Stefan Wilson (No. 25 Driven2savelives – KVRT Chevrolet) completed all three phases of rookie orientation, which included 10 laps in the range of 205-210 mph, 15 laps at 210-215 mph and 15 laps at 215-plus mph. Those who didn’t complete all three phases during the two hours were able to later in the afternoon.

Veterans taking the refresher needed to complete the final two phases. All five – Bell, Bryan Clauson (No. 88 Cancer Treatment Centers of America Honda), JR Hildebrand (No. 6 Preferred Freezer Fuzzy Vodka Chevrolet), Sage Karam (No. 24 DRR-Kingdom Racing Chevrolet) and Oriol Servia (No. 77 Lucas Oil Special Honda) – did so.