The Erebus driver was untouchable throughout the session, securing provisional pole by over a tenth of a second with a fast 2m04.664s.
Which means he’ll run final within the Prime 10 Shootout on Saturday night, which is able to decide the primary 5 rows of the grid.
It was a special story for Kostecki’s closest title rival Shane van Gisbergen, who solely rescued his Shootout hopes with the seventh quickest time on his final lap.
Brown, in the meantime, missed the Shootout altogether after a troublesome session that began with a visit into the Flip 2 tyre wall.
Brown was liable for a dramatic begin to the 40-minute session, the title contender firing his Erebus Camaro into the wall on his first run.
That prompted an early pink flag, Brown capable of get the broken automotive out of the tyre barrier and again to the pits to start repairs.
After a bit underneath 10 minutes the session went inexperienced once more with out a single consultant time on the board.
And no one might get a lap in earlier than the pink flag was again out, this time due to Fraser clouting the wall onerous at The Chopping, placing him out on the spot.
The second stoppage was a blessing for Brown, giving his crew time to restore his automotive and ship it again out only a few minutes after the subsequent restart.
When the occasions did begin to land they have been spectacular, Cam Waters turning into the primary driver into the 2m04s in a Gen3 automotive when he jumped to the highest with a 2m04.990s.
Initially he had Matt Payne a few tenths behind him, earlier than James Golding jumped into second with a 2m05.163s.
As soon as Kostecki lastly obtained a lap carried out it was much more spectacular, the sequence chief charging filter entrance with a 2m04.664s.
Each Golding and Anton De Pasquale have been capable of sneak into the 2m04s on their subsequent runs, Kostecki persevering with to carry a bonus of over a tenth of a second because the clocked ticked down.
The lead group did all head out for a closing run, nevertheless there have been no adjustments proper on the prime, Kostecki taking provisional pole forward of Golding.
Golding was the shock of the session along with his second place forward of De Pasquale and Waters.
Broc Feeney, one other driver nonetheless in rivalry for the title, was fifth quickest whereas David Reynolds ended up the very best of the Grove Racing automobiles in seventh after bettering on his closing lap.
Van Gisbergen spent nearly all of the session outdoors the highest 10, the Kiwi digging deep proper on the flag to finish up seventh, and preserve his hopes of pole place alive.
Brown and co-driver Jack Perkins will begin Sunday’s Nice Race from seventeenth with Brown unable to crack the very best 10 in his repaired automotive.
The 2023 Repco Bathurst 1000 continues with two extra observe periods at 10am (12am BST) and 1pm (3am BST) native time on Saturday, adopted by the Prime 10 Shootout at 5:05pm (7:05am BST).
Bathurst 1000 qualifying end result