The second quarter of the race kicked off with a fascinating battle at the front between Shane van Gisbergen (#888 Triple Eight Mercedes) and Matt Campbell (#912 Manthey EMA Porsche).
The Kiwi led the Aussie by around second until the the 3h30m when the safety car made its second appearance of the day.
The cause of the caution was a run-in between the #44 Valmont Racing Mercedes and the #47 Supabarn Audi at Skyline, which led to heavy contact with the wall for Aaron Cameron and the AMG.
That prompted a round of stops for much of the field, Manthey EMA opting for a shorter fuel fill to help Thomas Preining, who replaced Campbell, take over the lead from van Gisbergen.
When the race went green 15 minutes later Preining bolted at the front, pulling two seconds on van Gisbergen on the restart lap.
The gap steadied there, though, as van Gisbergen settled into a rhythm with Augusto Farfus (#32 WRT BMW), Maro Engel (#999 GruppeM Mercedes) and Sheldon van der Linde (#32 WRT BMW) in tow.
The green running only lasted 10 minutes, the safety car called on for a third time when Fabian Schiller came to a stop in the Hell Corner run-off in the #19 Nineteen Corporation Mercedes GT4.
This time the lead group all stayed out, the only notable stoppers the #75 SunEnergy1 Racing Mercedes and the #77 Craft-Bamboo Mercedes from sixth and seventh respectively.
The race went green again just after the four-hour mark, Preining again able to pull immediately clear of van Gisbergen.
The Triple Eight driver, meanwhile, had to stave off enormous pressure from Farfus on the restart lap, the pressure only relieved at the start of the second green flag lap when Farfus found himself under attack from Engel up Mountain Straight.
Farfus and Engel rubbed doors as they went side-by-side on the run to Griffins, the latter attempting a bold move around the outside as they got to the right-hander.
The move proved unsuccessful, though, Engel ending up too wide and letting van der Linde sneak into fourth place.
The lead group held station for the next 20 minutes, at which point Farfus started to put the pressure back on van Gisbergen. That pressure led to van Gisbergen running slightly wide at The Chase, Farfus able to get alongside the #888 AMG on the run to Murray's Corner, but unable to find a way past.
Van Gisbergen was then able to re-establish a small margin over the BMW until the 4h40m mark when the #888 entry became the first of the lead group to make a fourth stop.
It was at that point that Broc Feeney took over the car for the first time for the day.
Preining's lead was around six seconds when the top three cars all took their next service right on the five-hour mark.
Mathieu Jaminet took over the Porsche, retaining the effective lead as he resumed a couple of seconds ahead of Feeney.
Valentino Rossi took over the #46 entry, which resumed in what was effectively third, while Dries Vanthoor jumped in the #32 BMW.
A lap later Engel took his next stop, handing the #999 Mercedes over to Raffaele Marciello and leaving an out-of-sequence Luca Stolz leading the race in the #75 Mercedes.
Engel was able to get out ahead of the two BMWs, as did Daniel Juncadella in the #77 Mercedes when he took his next stop several laps later.
Stolz, who had quietly built up a gap of over a minute, then stopped on the 5h18m mark, Jules Gounon taking over the #75 Mercedes and resuming with the race lead and an 10s margin back to a battling Jaminet and Feeney.
Gounon had the measure of the chasing pack too, the gap over Jaminet easing out to 18s as the race ticked over the six-hour mark.
Feeney, meanwhile, pitted from third just before six hours, resuming in seventh and moving Marciello into third, Juncadella into fourth and Vanthoor and Rossi, who swapped positions midway through the stint, into fifth and sixth respectively.
The #777 Melbourne Performance Centre Audi leads the Pro-Am standings while the Cameron's earlier crash has left the #10 International Motorsports Audi in control of the Silver class.
