Will Power says IndyCar test pace shows performance gains

And the Australian reckons there is even more pace to come when teams switch to softer tyres.

Power ended the day with a best lap of 1m07.8625, and 24 of the 25 drivers went under the official Barber track record - also held by Power - of 1m09.8529s.

"[The times were fast because of] the work that was done during the year last year, and also engine work with the engine manufacturers," said Power.

"And it's a little cooler, which helps turbo and it helps grip. It's just a very fast situation.

"And remember, we're running on black tyres. If you can imagine when we put the [softer] reds on, it's going to be fast."

Power's Penske team-mate Helio Castroneves finished the day just behind him, and while Power was cautious about reading too much into test times, he said that the result is a good reward for the work that the team has put in during the off-season.

"It's only the first day of testing, but that shows that we worked hard in the winter," he said.

"As a team we're very determined to check a couple of boxes this year - obviously the Indy 500 and the championship are absolutely top of the list."