“Car has felt pretty good for most of the day. The first session we tried doing some stuff to our program, but we didn’t feel it was too comfortable," explained Mostert.
“I think the track has deteriorated over the last couple of years here and maybe the guys that test here know how much it’s deteriorated. For us, it didn’t feel like one of my best QR laps, but overall the time was impressive.
“I still think we need to work on our qualifying car. I hope everyone has the same imbalance through one and two and has a bit of understeer there.
"The bumps are the biggest they’ve ever been here so it’s going to be a challenging day tomorrow."
Shane van Gisbergen had led the way for the bulk of the 45 mins after matching McLaughlin’s Practice 1 pace-setting time on his first run.
It was a busy opening 15 minutes for the Red Bull driver, who had an off at Turn 3 and also suffered a puncture.
McLaughlin took over the front-running with four minutes to go before Rick Kelly, David Reynolds and eventually Mostert shot to the top.
Mostert ended up 0.1s clear of Fabian Coulthard, who jumped to second with his final flying lap.
Van Gisbergen also improved late to be third ahead of Kelly, Reynolds, Mark Winterbottom, Craig Lowndes, Lee Holdsworth, Cameron Waters and McLaughlin.
Scott Pye had gone second with two minutes remaining but ended up down in 12th, one place behind team-mate James Courtney.
Further back, Jack Le Brocq continued to set the pace among the wildcards in 18th with his MW Motorsport Nissan.
Jamie Whincup was two places further back in 20th and says his crew has work to do in tomorrow’s final practice before qualifying.
“We didn’t get a clean run so I don’t think we showed what we had,” he said.
“The car wasn’t that flash, but there’s no panic stations. We’ll make the car better tomorrow and I’m confident we should be somewhere there.”
Two seconds covered the entire 30 cars, with returnee Alex Davison 0.5s behind Lucas Dumbrell Motorsport team-mate Alex Rullo at the bottom of the order.