However, Whincup flew by soon after, and McLaughlin couldn't get past, eventually finishing 2.1s behind the veteran Australian.
Whincup also claimed the Triple Crown trophy, given to the best driver over the weekend's three races, after ending tied on points with Coulthard. Whincup earned the tiebreaker for his higher finish in the final race, where Coulthard finished fifth.
"That was a great battle," said Whincup after the second race. "That reminded me of the old 2017-18 days where we were going head-to-head with these boys.
"We just kept chipping away at the car all weekend and made it fastest for race three. I thought after the penalty yesterday, we were done and dusted for the Triple Crown, but fantastic to have a great day and get right up there."
The other Kiwi contender, Shane van Gisbergen, had a solid Sunday. He held off David Reynolds in an entertaining battle for fourth in the first race, having started from seventh, before rounding out the podium with third in the weekend's last showdown.
Supercars standings
1. Scott McLaughlin 1024
2. Jamie Whincup 923
3. Chaz Mostert 814
4. Shane van Gisbergen 753
5. David Reynolds 736
6. Cameron Waters 733
7. Mark Winterbottom 706
8. Nick Percat 705
9. Fabian Coulthard 682
10. Lee Holdsworth 675
11. Andre Heimgartner 602
12. Anton de Pasquale 583