NASCAR Sprint Cup star Brad Keselowski tries Penske's IndyCar

The 2012 Cup champion drives for Penske's Ford team in the stock car series.

He was given the chance to try Simon Pagenaud's Dallara-Chevrolet during the afternoon of a multi-team IndyCar test at the Elkhart Lake track, venue for the next round of the championship on June 24-26.

"First thing I told Simon [afterwards] is he has a very secure job, at least from me," Keselowski said.

"I've got a lot of respect for him and his team, everyone at Team Penske.

"Simon was fast, really fast, and gave me a good rabbit to chase.

"I learned a tonne and had a lot of fun. I've got to let it soak in to think about all of it."

Though the 32-year-old has spent his whole racing career in stock cars, he said testing an IndyCar had always been an ambition.

"I've always wanted to drive an IndyCar, I think [Penske president] Tim Cindric knew that," Keselowski said.

"The opportunity came up to dip my toes in the water and kind of expand my knowledge base and put it in the back of my mind for wherever it goes."

Pagenaud ran a few shakedown laps in the car before turning it over to Keselowski, who quickly noticed the difference in handling and braking potential.

"It sure was getting in the corners a lot deeper," Keselowski said.

"The Indycar just pulls so many Gs through the centre of the corner and in the brake zone.

"You have to build confidence in it because the stock car does everything it can to wreck your confidence and in the IndyCar it's important to have confidence.

"So you have to kind of unlearn everything you learned in a stock car to be good in these cars.

"That's a heck of a process but a fun one.

"It's certainly a different feel, trying to get acclimatised to a different seat and you lean back more.

"I was sitting in Simon's seat and it doesn't always fit you perfect, so it wears you out pretty quick. But it's a good way to get worn out."

Eleven IndyCar drivers participated in Wednesday's test, which comes ahead of the legendary 4.048-mile Road America track's first top-line single-seater event since the 2007 Champ Car season.