Tyres were there focus of the 40-minute session as teams and drivers got their first taste of the brand new super soft control tyre.
With question marks over the level of degradation, long runs were a focus for much of the field throughout the session.
That meant Mark Winterbottom’s early 1m06.334s, set on just his second lap, was the benchmark until the qualifying sims started with a few minutes to go.
At that point the times started to tumble, Anton De Pasquale first to knock Winterbottom off top spot with a 1m06.290s.
Cam Waters and Scott Pye then went close, slotting into what was second and third respectively, before Percat knocked every down a spot with a 1m06.169s at the flag.
“Yeah it felt good,” said Percat. “We had a very well-structured programme and we just stuck to it. We went through the changes we wanted and the end result was a pretty fast lap time.
“We made a change for our last run with new tyres and it actually really hooked up. Early days, but it was nice to have a drive on the super softs.”
Winterbottom ended up fifth with that early time, followed by Chaz Mostert, David Reynolds and James Courtney.
Todd Hazelwood and Jack Le Brocq rounded out the Top 10, while series leader Shane van Gisbergen was just 11th after changing a splitter early and running off track several times during the session.