Erebus Motorsport Chevrolet driver Will Brown has beaten Grove Racing Mustang pilot Matt Payne to Practice 1 bragging rights at the Repco Bathurst 1000 by 0.0071s.

The Ford Mustangs are competing this weekend with an unchanged aerodynamic package after the Supercars Board rejected a proposed parity adjustment which has caused a furore even into today.

It was not enough to stop Payne from splitting the Erebus Camaros of Brown and championship leader Brodie Kostecki although how much can be read into that in the context of the ongoing parity storm is unclear, given teams were on different practice programmes and some started the hour-long session with pre-marked tyres.

Brown clocked a best of 2:05.9653s and Payne a 2:05.9724s in the first official Gen3 session and the first on genuinely soft tyres at Mount Panorama, with Kostecki 0.1067s off the pace on a 2:06.0720s.

Walkinshaw Andretti United’s Chaz Mostert and Grove’s Reynolds rounded out the top five in two more Mustangs, the latter at 0.5032s away from top spot.

The field had rolled out at a cold, windy Mount Panorama and it was Erebus fastest immediately, Brown (#9 Coca-Cola Camaro) setting a 2:07.6653s and Kostecki (#99 Coca-Cola Camaro) a 2:08.2893s on their first flyers.

Kostecki was a full second clear of his team-mate, and the rest of the field, when he laid down a 2:06.0720s next time through, and backed it up with a 2:06.1722s on his third lap, by which time the Shell V-Power Racing Team’s Anton De Pasquale had moved to second on a 2:06.9045s in the #11 Mustang.

Brown restored the Erebus one-two with a 2:06.3441s on his second run, then moved to the top with the aforementioned 2:05.9653s during this third run, as David Russell enjoyed seat time in the sister #99 entry.

With just over 10 minutes to go, Payne elevated the #19 Penrite Mustang to third position with a 2:06.1233s which included new fastest second and third sectors.

On his following lap, the New Zealander took over second spot with a 2:05.9724s despite being slower in those latter two sectors.

With the chequered flag out, two-time Bathurst 1000 winner Mostert jumped from 14th to fourth on a 2:06.2075s in the #25 Mobil 1 Optus Mustang and 2017 Great Race winner Reynolds wheeled the #26 Penrite Mustang to a 2:06.4685s.

Scott Pye (#20 Toyota Forklifts Camaro) ended up sixth from last month’s Sandown 500 winner, Broc Feeney (#88 Red Bull Ampol Camaro), on a 2:06.5899s.

De Pasquale was classified eighth, from Andre Heimgartner (#8 R&J Batteries Camaro) and seven-time Great Race winner Craig Lowndes (#888 Supercheap Auto Camaro) in the Triple Eight Race Engineering wildcard.

James Moffat had a late tour up the Murray’s Corner run-off area in Cameron Waters’ #6 Tickford Racing Mustang which ended up 13th-fastest, while Shane van Gisbergen had a similar excursion in the #97 Red Bull Ampol Camaro on his way to 15th.

Wildcard Aaron Love (#7 Petronas Mustang) had two offs at The Chase and James Courtney (#5 Tickford Mustang) one, while two-time Bathurst 1000 winner Will Davison came extremely close to scraping the #17 Shell V-Power Mustang on the wall on the run to Reid Park, but the session ran uninterrupted.

Fastest sectors belonged to Kostecki in the first; Mostert in the second, which covers most of the run ‘across the top’; and Reynolds in the third, which is dominated by Conrod Straight.

Primary drivers enjoyed the majority of running, although a number of co-drivers were also handed seat time.

Practice 2, an hour-long session for co-drivers only, starts this afternoon at 16:50 local time/AEDT.

CLICK HERE for full Practice 1 results