Juan Pablo Montoya continued his readjustment to IndyCar at Phoenix on Tuesday when he completed his first oval test since joining Penske.
The Colombian, who had his first outing with the team at Sebring last month, took the wheel after an initial shake-down by Helio Castroneves.
He admitted that the cornering speeds took some getting used to after so many years in NASCAR.
"My first impression was when Helio started running," he said. "We did some laps in the road car and I said, 'in NASCAR we brake here and here.'
"He was like, 'No, this is going to be wide open.' I'm like, 'What?'
"In the straight it just goes fast, but you don't really realise how fast it's going until he turns and the thing just snaps into the corner.
"And then you like into [Turns] 3 and 4 and, wow. Your foot never moved.
"For me, the big difference is the entry to the corner. Once you get to the middle of the corner, whatever speed you have, you are committed to.
"You just want to build to it and get comfortable with the feel. I'm still understanding what the car wants and what I want out of the car.
"You forget how fast an open-wheel car is - around 6.0s quicker than a [NASCAR Sprint] Cup car [over] a lap [around Phoenix]."
Montoya will join Castroneves and Will Power for the Chevrolet manufacturer test at Sebring next month, and will run again in the open test scheduled at Barber in mid-March.
The season begins in St Petersburg on March 30.