It was a different story for teammate van Gisbergen (#97 Red Bull Ampol Camaro), who picked up a kerb strike at Turn 7 on his final run and bowled a wide at Turn 9.
Van Gisbergen was unable to improve on his second push lap, and ended up just 19th in the 27-car field.
The 20-minute session was held under more sunny skies in Melbourne, with Kostecki benefiting from a tow from Brown to clock a 1:08.4550s, the time holding firm for the remainder of the session.
There were six Ford Mustangs in the top 10, led by Tickford Racing driver Thomas Randle (#55 Castrol Mustang) in fourth position, at 0.2514s off the pace.
CoolDrive Racing driver Todd Hazelwood, the 2017 Super2 champion, was an impressive fifth despite setting his best time before his rivals rolled out for the final runs.
Brown sat second after his first flyer on a 1:08.7494s before having an off at Turn 1, before later improving in the final runs with a 1:08.5585s.
Both Red Bull Ampol Camaros only rolled out for the first time with 12 minutes remaining, with Feeney moving up second place with a 1:08.7475s.
Brown improved, before Feeney did again with a 1:08.5833s — only for Brown to improve again with a 1:08.5585s. Kostecki sat out the middle part of the session with Brown forming an Erebus one-two, ahead of Feeney and Randle.
Will Davison (#17 Shell V-Power Mustang) Cam Waters (#6 Monster Energy Mustang), Jack Le Brocq (#34 Truck Assist Camaro), David Reynolds (#26 Penrite Mustang), Matt Payne (#19 Penrite Mustang and Tim Slade (#23 Nulon Camaro) completed the top 10.
Hazelwood moved from 19th to fifth with a 1:08.7177s in the #3 CoolDrive Mustang as he enjoyed the track to himself before the final runs commenced.
Behind them, notables Andre Heimgartner (#8 R&J Batteries Camaro) were 15th, Chaz Mostert (#25 Mobil 1 Optus Mustang) in 16th, and van Gisbergen in 19th.
As the final runs began, James Golding (#31 Nulon Camaro) had an off at Turn 1, with van Gisbergen picking up a Turn 7 kerb strike before running off at Turn 9.
Van Gisbergen, who is racing with Richie Stanaway, managed to get another lap in, but couldn’t improve and ended up 19th.
Reynolds improved from ninth to sixth with a 1:08.7345s on his final run, ahead of Davison, Waters, Le Brocq and Payne, both Penrite Fords scoring Shootout berths.
Slade missed out and will share the 11th row with the Cameron Hill/Jaylyn Robotham (#35 Truck Assist Mustang) entry.
Heimgartner/Dale Wood are set to start 15th, ahead of Mostert/Lee Holdsworth 16th, and Anton De Pasquale/Tony D’Alberto (#11 Shell V-Power Mustang) 20th.
The ARMOR ALL Top Ten Shootout will commence at 5:20pm AEST on Saturday afternoon.
The finishing order of the Shootout will set the grid for Sunday's 500km feature event, which will commence at 2:15pm.