The race got underway in unique circumstances, the safety car leading the field for a lap before releasing the cars single-file.
That was part of the mitigation measures put in place by Supercars following two seperate engine fires on Friday and Saturday.
Polesitter Feeney led initially, although starting on the hard compound Dunlop meant he would always be a sitting duck.
He was quickly swamped by both super softs-clad Mostert and Will Brown who dived either side of the Red Bull Camaro on the first green flag lap.
Feeney and the rest of the hard runners, including Andre Heimgartner and Brodie Kostecki, all dived into the pits at the end of that first green flag lap to take on the super soft tyres.
That left Mostert leading Brown until Lap 4 when the Erebus driver made a play for the lead on the outside of Turn 13.
It proved to be unsuccessful, though, Brown losing control of his Camaro on the exit of the corner and spinning into the wall.
Mostert then led Bryce Fullwood until Lap 8 when a clearly quicker Fullwood dived into the lead at Turn 1.
As Fullwood pulled away things got worse for Mostert, who was swamped by Will Davison, Shane van Gisbergen and Jack Le Brocq on the next lap.
What later proved to be a blistered tyre saw him drop even further back in the field before he stopped.
At the same time the early stoppers started to emerge in the picture with the likes of Feeney, Heimgartner and Kostecki closing to within a stop of the lead, despite being at the back end of the top 10 on the road.
When the top eight all took their mandatory service on the penultimate lap the early stop strategy paid off.
Feeney rocketed through to the lead from Heimgartner and Kostecki, with Fullwood dropping to fourth ahead of van Gisbergen.
Fullwood's day then got worse during the stops, contact with Mark Winterbottom in the lane drawing a 15-second time penalty.
There were no changes at the front on the final lap, Feeney scoring a second career victory by just under a second from Heimgartner.
"When I survived the first lap, and I was nearly faster than [Mostert and Brown] over the back, I was like, 'this is good'," said Feeney.
"I let Chaz and Will go and tried to slot in behind them.
"Fresh air was awesome. This morning it was a flip of the coin as to what we were going to do, but we certainly made the right strategy.
"What a way to win, Grand Prix Sunday. I've dreamt about this for a long time."
Third place for an in-form Kostecki meant he walked away with the Larry Perkins Trophy.
The Erebus driver also took over the series lead from Mostert who struggled to 14th thanks to that tyre issue.
Fullwood crossed the line in fourth but was demoted to 18th thanks to his penalty.
That promoted van Gisbergen to fourth ahead of Le Brocq, Davison, Macauley Jones, David Reynolds, Todd Hazelwood and Cam Waters.
The 2023 Supercars season continues with the Perth SuperSprint on the last weekend in April.
