Unlike the previous three sessions, there was no early burst of speed as tricky track conditions left Will Brown's 2m06.010s as the early benchmark.
That was partly thanks to series leader, and Erebus teammate, Brodie Kostecki running off the road at The Chase on his first run.
Kostecki had another crack at a time on the 20-minute mark, a cleaner effort yielding a 2m05.617s to go fastest.
Having done the lion's share of practice 3, Kostecki then handed his Coca-Cola Camaro over to co-driver David Russell for the middle part of the session.
Kostecki returned to the wheel for the final few minutes as teams shifted their focus to qualifying runs.
By that stage drivers were already chasing down his time, the likes of Scott Pye, Chaz Mostert and Cam Waters all going close.
None of them could get close enough, though, with only one driver able to beat Kostecki's early time – Kostecki himself.
He put a remarkable six-tenths of a second on the field on his final run, a 2m05.121s the fastest lap of the weekend so far.
Pye was best of the rest in second ahead of Mostert and Waters.
An in-form Matt Payne was the only other driver within seven-tenths of Kostecki, improving twice on his final run to drop into fifth.
Anton De Pasquale was sixth fastest ahead of James Golding, Thomas Randle, Broc Feeney and Jack Le Brocq.
Brown was shuffled back to 11th amid the late improvers, while it was another tough session for Shane van Gisbergen, who was 17th fastest.
The Kiwi had looked set to improve twice on his final run, a lock-up into the Elbow ruining one lap, before he out-braked himself into the last corner on the next.
Qualifying will take place at 4:15pm local time and will determine grid positions 11 to 28.
The fastest 10 drivers will then do battle for pole in the Top 10 Shootout tomorrow evening.
