Whincup looked to have the advantage over the Mercedes-AMG entering the final stint of the race, thanks to a blistering stint from co-driver Vilander, however van Gisbergen's STM outfit issued one final roll of the dice in pitting the Kiwi just for tyres.
What followed was a valiant defence from van Gisbergen once Whincup and his fresh tyres had caught him. When Whincup pushed on the outside of van Gisbergen on Conrod straight with 40 minutes to go, the reigning Supercars champion shepherded Whincup to the edge of the track and then to the grass. Whincup eventually sealed the crucial move to claim the victory for the Ferrari squad.
"It was a fantastic day, it was fantastic team work, we pitted at the right times. The blokes besides me did an amazing job and it was just up to me to bring it home at the end," said Whincup.
"It was quite ironic that me and my teammate [van Gisbergen] were fighting for the win right at the end there. He was driving like he usually does, all over the place, which is good - he's hard and fair.
"Certainly enjoyed the battle, there is always a bit of grass action when we're rubbing panels."
A saving grace for both Maranello Motorsports and STM was that almost every other major contender for the race also encountered their own share of problems.
Both Jamec Pem Audis, both Nissan Motorsport GT-Rs, both M-Sport Bentleys, and both Tekno Autosports McLarens ran into troubles early (with one Tekno McLaren failing to even make the start due to damage sustained on Saturday). Add to that also the factory Porsche 911 GT3 R driven by Kiwi Earl Bamber, Laurens Vanthoor, and Kevin Estre, which retired early with suspension damage.
This held the door open for the Maranello Ferrari and STM AMG to duke for the win, even though both cars incurred pit-lane penalties during the race.
The Ferrari team received their drive-through penalty for weaving during a safety car period, while the AMG team got theirs after van Gisbergen's teammate Craig Baird made contact with the Ferrari during a race restart.
But while the spoils went to the Ferrari team, the STM crew failed to finish the race, after a chaotic final 30 minutes overshadowed the team's weekend.
While trying to keep in touch with Whincup, van Gisbergen made contact with the lapped Porsche of Andrew MacPherson while navigating Caltex Chase. This sent MacPherson into the concrete wall and resulted in van Gisbergen incurring the team's second drive-through penalty of the day.
However the penalty would never come to pass, after van Gisbergen crashed later on during the lap that the news was brought to light. Exiting The Dipper, van Gisbergen slid sideways and into the wall, giving his AMG terminal frontal damage and ending the team's race.
Van Gisbergen's co-driver Maro Engel was critical of his teammate's driving during a television interview following the crash.
"That's not motorsport in my book," he said.
"I've got to watch out what I'm saying, but all I've seen this weekend is a lot of mistakes from Shane. It's a tough one."
He later apologised for the comments, acknowledging that van Gisbergen had apologised for the race-ending incident.
Van Gisbergen's crash promoted the Competition Motorsports Ice Break Porsche 911 GT3 R to second place, helping gift 21-year-old Matt Campbell - who will partner with van Gisbergen at this year's Pirtek Enduro Cup - his first finish on the overall 12 Hour podium along with teammates Patrick Long, David Calvert-Jones, and Marc Lieb.
Bentley's sole finishing car, the #17 entry of Stephen Kane, Oliver Jarvis, and Guy Smith rounded out the podium, finishing ahead of Walkinshaw GT3's giant-killing combination of Liam Talbot, John Martin, and Davashen Padayachee - who also won the honours in the Am class.
It was a largely forgettable race for the bulk of the New Zealand contingent. Along with van Gisbergen, Baird, and Bamber's failure to finish, the privateer efforts of Kiwi Racing and Sam Fillmore also failed to finish, as did GT3 debutant Andrew Waite - who didn't even get in the car after a crash between car owner Tony Quinn and BMW Team SRM's Steve Richards ruled them out early.
Dominic Storey, along with co-drivers David Reynolds and Mark Griffith, had good pace, but reliability wasn't on their or their Mercedes-AMG GT3's side, and they too would miss out on the chequered flag. Things weren't much better for Chris Pither, who limped home to 31st after an unlucky and rough debut race with Hobson Motorsport.
In fact, out of the 14 New Zealanders on the grid, only four made it to the finish line - Pither joined by Simon Evans, Daniel Gaunt, and Matt Halliday.
Evans, along with Audi co-drivers Marcus Marshall, James Koundouris, and Theo Koundouris, had a quiet run for much of the race, and eventually finished in 11th overall - fourth in the Am class.
Gaunt and Halliday, who shared an Audi R8 GT3 with Ash Samadi, ended up finishing seventh overall and third in the Pro/Am class. They also racked up the achievement of first Audi to finish.
