Three teams cracked 100 laps of testing through six hours of official pre-season testing at Winton on Friday.
With two hours remaining, the #6 Monster Energy Mustang, the #20 DEWALT Racing Commodore and #8 R&J Batteries Commodore registered 108, 104 laps and 100 respectively.
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The #5 Truck Assist Mustang (96 laps) and #2 Middy's Electrical Commodore (91) from Tickford Racing and Walkinshaw Andretti United respectively lurked just behind.
Will Brown's quick time from the morning remained atop the time sheets, with the Erebus Motorsport rookie's 1:19.5089s holding firm as the heat settled at Winton.
The session was red-flagged after 1400 local time after Thomas Randle ground to a halt in the infield.
It was later revealed a wheel nut had come loose, causing a wheel to come off the car.
The #44 Boost Mobile Mustang was quickly repaired, and the car returned to the track shortly afterwards with primary driver James Courtney behind the wheel.
Andre Heimgartner's #7 NED Whisky Kelly Grove Racing Mustang had completed the fewest laps through six hours with 47.
The 2021 season will commence at the Repco Mt Panorama 500 next weekend.
Tickets for the event are on sale now.