The Walkinshaw TWG Racing star backed up his Saturday victory with a third place in the second race, although it was far from straight forward.
Mostert charged from eighth on the grid to third and was closing on leaders Broc Feeney and Brodie Kostecki with 15 laps remaining.
That’s when he was asked by engineer Sam Scaffidi to drop back to help teammate Ryan Wood’s bid to make it through to the next round of the finals.
“We need you to be a good teammate and help Woody out behind. We need you to start falling back,” said Scaffidi, to which Mostert replied, “Mate, these guys are just there. Is it going to make a difference or not?”
Radio communications played on the TV broadcast depicted an angry Mostert pushing back on the instructions, yelling “for f***’s sake” when told Wood was 11 seconds behind.
When pressed further by Scaffidi to “drop it back” with 13 laps to go, Mostert’s voice raised again.
“What? You want me to come back again now, are you sure?”
The response was particularly eyebrow-raising as Wood memorably helped Mostert to the title last year in the first running of the finals format.
Mostert’s Gold Coast gift put Wood in position to secure a Sandown berth, before late pit stops for two Chevrolets swung the battle back in Anton De Pasquale’s favour.
Asked post-race if he was frustrated about having to help out Wood, Mostert turned the focus onto his own mistake in the Top 10 Shootout.
“My frustration, if there was any in the race, is still kicking myself about qualifying,” he said.
“When you’ve got the fastest car, you’ve got to execute, and especially in these final situations.
“That mistake in the Top 10 [Shootout]… I was super-frustrated for the start of the race and sometimes that works in my favour, or sometimes it doesn’t.
“When you come from ninth or eighth on the grid, you give everyone a little bit of a head start.
“It would have been nice to put some more pressure on a bit earlier.”
Despite ultimately missing the cut, Wood publicly thanked Mostert for his help post-race, saying “that shows the sort of human he is”.
Mostert is now preparing to go to Sandown with Wood playing the wingman role that the Kiwi so perfectly executed at the Melbourne event 12 months ago.
“I’m very lucky. I’ve got one of the most talented teammates in the category,” Mostert said.
“His development over the last, especially 18 months, nearly two years, watching his feedback, how crucial he is in taking our cars to the next step and getting faster is what we’re going to be leaning on going to Sandown.
“I’m still pretty gutted that he’s not here in the semis because of how fast he is, how talented he is, he deserves to be in there.
“So, a bit like last year, which was deja vu, [I’ll] put that weight on my shoulders and try and do it for our team.
“I know that he’ll give it his all and give me as much help along the way.”