Fernando Alonso said he was satisfied with an "amazing" first day of official practice for the Indianapolis 500.
The McLaren driver, who is racing at this year's event on 28 May instead of at the Monaco Grand Prix, was 19th on Monday with a 223.025mph average.
"Everything went very smoothly," said the 35-year-old Spaniard, who is a two-time F1 world champion.
"The last half-an-hour we had some issues with the rear suspension and we could not complete the programme."
He added: "We had planned to run a little bit in traffic, so we missed that part, but overall it was an amazing day."
Alonso has a race against time trying to learn all the intricacies of car set-up and racing on a 2.5-mile superspeedway against drivers who have been doing it for years.
He said he felt he had made progress since his first run at Indy when he completed his rookie test two weeks ago.
"The car felt as good as it did at the test, and I was able to make some set-up changes without losing the confidence in the car," Alonso said.
"I'm happier than the first day with the car because I was able to feel some of the set-up changes that we were planning in the morning.
"We did not do much running in traffic, so that's still the thing that I need to go through in the next couple of days.
"But I did two or three laps behind some cars that were going out of pit lane, and it was good fun."
Marco Andretti, Alonso's Andretti Autosport team-mate, was fastest at 226.338mph on the first of five days of practice before qualifying this weekend.
"In my case, qualifying is not very important," Alonso added.
"When you are out there, you want to feel fast so it's a question of enjoyment, not only the final position.
"But I think the priority for us in my garage is to set up the car for the race, to feel comfortable in traffic, to learn as much as I can, the way to overtake, the place to overtake, how you lose the minimum momentum in those manoeuvres.
"There are many things that I don't know now and I need to learn quickly. So let's see what we can do in qualifying. But definitely, the race preparation will be the first priority."