The long-predicted wet weather finally arrived for the fourth hour-long session, with rain falling for the duration.
Will Davison initially led the way with a 2m35.451s before van Gisbergen lowered the benchmark to a 2m31.992s.
When the session resumed it was Richie Stanaway that charged to the front. The Kiwi, making his first Supercars start since the end of the 2019 season, first went second quickest with a 2m32.183s.
He then jumped van Gisbergen with a 2m31.840s shortly afterwards.
The session was red flagged for a second time at the midway point of the session after Macauley Jones went off at The Chase, brushed the wall and then ended up stranded in the sand.
Once the session was green again there was a fascinating battle between the two lead Triple Eight cars.
Van Gisbergen went fastest with a 2m31.603s only to be immediately usurped by Jamie Whincup in the #88 entry, who set a 2m31.296.
Van Gisbergen hit back on his very next lap, though, pulling a second clear of Whincup with a 2m30.292s.
Moments later the red flag appeared for a third time after Will Brown swiped the wall at The Cutting.
That proved to be the end of the session, race control opting to declare the session before the Erebus Holden had been retrieved.
James Courtney jumped to third fastest right before the red flag, which demoted Stanaway to a still-impressive fourth place.
That was a welcomed result for the Kiwi after two earlier sessions were hampered by mechanical issues.
"It's great to have a better session. We went from the bottom of the timing screen to the top," said Stanaway.
"I would have preferred to have some good laps in the dry to see what the car is capable of, but it looks like we might not get that.
"But it's good to get some laps in before qualifying because it looks like we might be in the same conditions."
Will Davison and Craig Lowndes rounded out the best 10, the latter surviving a hairy moment at pit entry when he aquaplaned into the mud and water blasted the front grill off his Commodore.
The Bathurst 1000 action continues with qualifying at 4:15pm local time.
Shane van Gisbergen
|Holden Commodore ZB||14||2'30.2922|
|Holden Commodore ZB||15||2'31.2961||1.0039|
|Ford Mustang GT||15||2'31.7691||1.4769|
|Holden Commodore ZB||13||2'31.8404||1.5482|
|Holden Commodore ZB||14||2'31.9747||1.6825|
Anton De Pasquale
|Ford Mustang GT||14||2'31.9992||1.7070|
|Ford Mustang GT||12||2'32.1132||1.8210|
|Holden Commodore ZB||14||2'32.1815||1.8893|
|Ford Mustang GT||14||2'32.2198||1.9276|
|Holden Commodore ZB||14||2'32.4520||2.1598|
|Holden Commodore ZB||15||2'32.4702||2.1780|
|Ford Mustang GT||14||2'32.5555||2.2633|
|Ford Mustang GT||14||2'32.6845||2.3923|
|Holden Commodore ZB||3||2'32.8581||2.5659|
|Holden Commodore ZB||12||2'32.9217||2.6295|
|Ford Mustang GT||12||2'33.1430||2.8508|
|Holden Commodore ZB||15||2'33.3153||3.0231|
|Ford Mustang GT||12||2'33.5595||3.2673|
|Holden Commodore ZB||10||2'34.3103||4.0181|
|Holden Commodore ZB||13||2'34.6340||4.3418|
|Holden Commodore ZB||14||2'34.9993||4.7071|
|Holden Commodore ZB||12||2'35.2556||4.9634|
Jack Le Brocq
|Holden Commodore ZB||12||2'35.7509||5.4587|
|Holden Commodore ZB||8||2'35.7535||5.4613|
|Ford Mustang GT||6||2'35.9665||5.6743|
|Holden Commodore ZB||12||2'36.5920||6.2998|
|Holden Commodore ZB||12||2'36.5950||6.3028|
|Holden Commodore ZB||8||2'37.9358||7.6436|
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