INDIANAPOLIS (AP) - After Marco Andretti jumped atop the speed chart during Monday's first Indianapolis 500 practice, he tried to put the brakes on the expectations.
The 29-year-old driver from one of the world's best-known and most cursed racing families turned a fast lap of 228.978 mph on the 2.5-mile oval, leading the way for a four-car sweep by Andretti Autosport drivers.
"It's definitely too early to get confident or to read into things," Andretti said. "Today is a picture perfect day and next week it's going to be like 83 or 84 (degrees) and that will change things completely, so you can't read too much into this at all."
Andretti's promising start was a dramatic change in what has been a challenging season. After five races, the son of team owner Michael Andretti still has not qualified or finished in the top 10.
Marco Andretti wasn't the only big surprise at Indy.
Honda outdueled rival Chevrolet by taking each of the top four spots and six of the top eight. Colombia's Carlos Munoz was second at 228.945, 2014 Indy winner Ryan Hunter-Reay was third at 228.033 and rookie Alexander Rossi was fourth at 226.865. Andretti's fifth driver, Townsend Bell, finished sixth at 226.724.
New Zealand's Scott Dixon had the best Chevy. The four-time series champ from Target Chip Ganassi was fifth at 226.835.
But the hardest part of deciphering what happens early in practice is figuring out what strategies teams are using. And with a 60 percent chance of rain today, Andretti acknowledged his team did things a little differently than others might have.
"We moved things forward on the test plan," he said, noting the gloomy forecast. "So I think we'll see how things shake out."
Qualifying for the 100th running of the 500 will be Saturday and Sunday. The race is scheduled for May 29.
Who's hot: Graham Rahal. The Ohio native has already had a solid month at Indy. He qualified third for the Grand Prix of Indianapolis, and after being pushed to the No. 24 starting spot because of a failed post-qualifying inspection, Rahal still managed to finish fourth. On Monday, Rahal produced the best Honda speed by a non-Andretti driver. He was eighth at 225.326.
Who's not: Buddy Lazier. At one time, the 1996 Indy winner seemed to be a master of this track. He produced five straight top-seven finishes from 1996-2000. But the 48-year-old Colorado resident has struggled there lately. In 2013, he started 32nd in the 33-car field. In 2014, he qualified 33rd. Last year, he missed the field and Monday he completed only seven laps and had the slowest car on the track at 212.641.
Rookie roundup: Each of the five rookies trying to make the race passed all three phases of their rookie orientation. Rossi was the fastest rookie of the day.
New number: Ganassi driver Charlie Kimball announced Monday he would change his car number for this year's race. Instead of donning the usual No. 83, he will switch to No. 42 as a tribute to Kyle Larson's cousin, who like Kimball is diabetic, and to help make the sales pitch for a new insulin product for adults called Tresiba. After taking one insulin injection for eight consecutive days, sponsor Novo Nordisk said the product stays in the system for 42 hours. Novo Nordisk will donate $4,200 to diabetes associations in Indiana and Charlotte on behalf of whomever leads each of those May 29 races on Lap 42. Larson races for Ganassi's NASCAR team.
Up next: Six more hours of practice today. Drivers are scheduled to be on the track from 11 a.m.-5 p.m.